Tag Archives: noninvasive prenatal screening

Are We Ready For This?

Recent advances in genetic testing technology have us poised on the brink of a new paradigm of prenatal diagnosis – prenatal screening for all genetic and chromosomal conditions. Okay, not all disorders, but lots. Non-invasive Prenatal Testing (NIPT), whole exome sequencing, and expanded carrier screening are close to being available and affordable to a large proportion of the population. This is the culmination of a trend that began with the introduction of amniocentesis in the late 1960s, followed by ultrasonography, maternal serum screening, microarrays, and cell free placental DNA in maternal serum. From a strictly technical standpoint, each technology, while far from perfect, was an improvement on its predecessors in terms of accuracy, detection, false positive rates, and the range of  detectable genetic conditions.

On the surface, this sounds like progress, and it is, in many ways. These technologies can contribute to the reduction of the incidence genetic conditions, some of which are pretty serious, a long-standing goal of medical genetics since its inception, as Nathaniel Comfort has pointed out. But technological advances often outstrip the ethical and social means with which to appropriately assess, modify, and utilize them in fair, just, and meaningful ways. So I ask these questions of the sage and thoughtful readers of The DNA Exchange: Just because we can perform prenatal screening for nearly everything genetic, should we? Who should be making this decision?

There are many competing and intertwined narratives about the history of prenatal diagnosis. Let me offer one such narrative to provide ethical and historical angles. During the 1970s and early 1980s, amniocentesis was primarily offered to women of “advanced maternal age” because of the well-documented increase in the incidence of trisomy with maternal age. At the time, in the US women 35 and older represented about 5% of the pregnant population, and this group accounted for about 20% of pregnancies with Down syndrome (this statistic has since changed considerably). While such a policy could be viewed as discriminatory and prejudicial against people with disabilities, the goal of the policy did not seem to be the elimination of genetic disability. Rather, the effect and likely the intent of the policy was to level the reproductive playing field for “older” mothers. During the 1970s, women made great strides in expanding their social and economic opportunities and in taking some measure of control over their reproductive lives with birth control and the availability of safe, legal abortion. Women could now readily attend most colleges and graduate schools, had more career opportunities, and did not feel as much social pressure to retire to motherhood after high school. However, one of the perceived obstacles for delayed childbearing was the greater risk of Down syndrome and other trisomies. Amniocentesis removed this perceived obstacle and consequently women felt freer to delay childbearing until such time as they felt that they and their partners were ready.

Over the decades, mission creep worked its way into prenatal screening. With the gradual incorporation of ultrasound and maternal serum screening into most pregnancies, regardless of maternal age, the detection rate for Down syndrome increased, and critics of prenatal diagnosis raised the specter of the theoretical elimination of all people with Down syndrome. While such an outcome never seemed likely for a variety of social, cultural, individual, and economic reasons, that could be viewed as the intent of prenatal screening. But still, aneuploidy represents only a small portion of all genetic and congenital disorders.

But it is a qualitatively different ethical story with universal NIPT and the expanding number of conditions it can screen for, the prospect of carrier screening for hundreds of genetic conditions for all couples, and talk of whole exome screening of fetuses. That is making quite a profound statement to and about people with a wide range of physical and developmental abilities.

We tacitly assume that the majority of pregnant women want such screening at the same time that we offer it to them. Many patients will  assume that because we are offering it, it must be a good thing. Because genetic counselors’ jobs can depend on the offer and uptake of such services, it affects our views and actions in ways that we often cannot fully appreciate or grasp. To some extent, we offer new testing because labs are offering it and because genetic counselors tend to be early adopters of new genetic tests. As much as we like to think that we are objective assessors of genetic technology who always put the best interests of patients first, the complicated human psyche makes for a messier reality. Our perspectives are distorted by being in the center of the storm. Go ahead and disagree with me if you want, but you are by and large wrong. That’s not me trying to sound superior; motivated blindness is a basic foundational principal of human psychology.

Psychological complexity aside, think of this. The medical profession is already doing a less than stellar job of presenting a realistic and unbiased picture of Down syndrome to parents. Remember, too, that more and more prenatal genetic testing happens without the involvement of a board certified genetic counselor and that parents are often not educated about these conditions until after they have received an abnormal test result. Not exactly the best time to seek out and weigh complicated information. Add a few hundred more conditions less common and familiar than Down syndrome, and you can see the makings of a goddamn mess.

So can there ever be an ethical justification for universal prenatal screening of (theoretically) all genetic and chromosomal diseases? Let me offer some suggestions that could serve as a starting point to address this question. One can argue that this framework or one like it should have been in place decades ago. I agree, it should have. I recognize that for people who are opposed to termination of pregnancy under any condition or for some of the staunchest disability advocates, prenatal screening will never be acceptable unless it somehow improves the lives of people with different abilities and their families. But I ask all sides to at least hear me out.

First, many parties should be involved in the discussion about wide scale prenatal testing, à la Cyprus and thalassemia screening. Prospective users, clinicians, labs, ethicists, religious leaders, legal experts, legislators, and most especially the community of people who are affected directly by the conditions in question (let me add “and others” since no doubt I am forgetting some important stakeholders). You will never get everyone to agree on all of the details, but there should be at least broad consensus about the most critical issues among the majority.

Second, more resources need to be devoted to improving the lives of people with genetic conditions and their families. Every newborn should  be able to live full, rewarding, loving, and enjoyable lives as much as humanly possible. This involves large-scale medical, technological, and social innovations and changes. Improving the social attitudes toward disability is a long, slow, frustrating journey but that should not deter us.

Third, related to the above, prenatal genetic testing should also offer some benefit people with the conditions in questions and their families, other than letting them have the same option as everyone else to terminate pregnancies. Right now, people with disabilities and their families get essentially zero benefit from prenatal screening. Or more accurately, very little research has been done to show any benefits.

Fourth, any new technology or test needs to be vetted by those who do not have a vested professional, financial, or personal interest in the technology or test. Intellectual, research, and financial conflicts of interest have ways of distorting our views in subtle ways that we are incapable of appreciating. This is extraordinarily difficult for us to understand and acknowledge (vide supra motivated blindness).

Fifth, better resources need to be developed for parents to become educated about the medical implications of genetic diagnoses, the range of developmental outcomes, the resources available to manage the condition, and the impact on families, particularly in lower socio-economic populations.

Sixth, this information needs to be provided to parents before they decide to enter the cascade of prenatal screening, not after they receive an abnormal test result. Parents have to carefully decide which if any condition(s) is important to their reproductive and family planning.

If all of these recommendations are in place, this will allow parents to make informed choices about whether or not they wish to go down the prenatal screening pathway and for which conditions. For parents who would never consider a termination under any conditions, they should have the option of screening only for those conditions for which prenatal knowledge can help the child and family, with better medical, psychological, or adaptational outcomes. For parents who have carefully weighed these issues and feel that there are certain conditions that they will choose to avoid if they can, then they should be supported in their decisions with safe, legal, and non-judgmental abortion services. For parents who are not interested in prenatal screening, they should be supported in their decision rather than being made to feel like they are sub-standard parents.

We can ignore my plea, just sit back and see what happens. But this would be a big mistake. Although genetic counselors obviously cannot address this issue by themselves, we are in the ideal position to take the lead in organizing, coordinating, and spearheading the discussion. We owe it to ourselves and to our patients.

 

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Guest Post: PPV Puffery? Sizing Up NIPT Statistics

by Katie Stoll and Heidi Lindh

Heidi and Katie are genetic counselors and both work with the newly established charitable nonprofit, the Genetic Support Foundation (twitter @GeneticSupport), geneticsupportfoundation.org.

The importance of the Positive Predictive value (PPV) in interpreting Noninvasive Prenatal Testing (NIPT) results is increasingly on the minds of providers as evidenced by frequent discussions, presentations, and publications on the topic. But what if, in an effort to make their lab look like the best lab, the NIPT PPV was overstated in marketing materials or even on test reports? And what if providers and patients believed this information without question or further investigation?

Until 2014, four labs (Sequenom, Verinata Health/Illumina, Ariosa and Natera) were the only companies in the United States that offered NIPT. Over the past year, we have seen a burgeoning of new labs offering their own branded NIPT tests. In some cases, the 4 original companies act as “pass-through” labs in which the testing is branded and advertised through a secondary lab however the sample is ultimately sent to the primary lab for analysis and interpretation. In other cases, referral labs have brought NIPT testing in-house, developing their own algorithms and reporting, such as the case for the InformaSeqTM test offered by LabCorp and Integrated Genetics. In a recently published marketing document, Illumina lists 16 laboratory “partners” that all offer a version of the Illumina NIPT. The other primary NIPT labs are also distributing their tests through other labs as well; Quest Diagnostics and the Mayo Clinic have been secondary labs for the Sequenom NIPT (Quest also has their own brand, the “Q-Natal Advanced”and Natera’s NIPT is available through GenPath and ARUP).

The growing number of laboratories that offer some version of NIPT presents a significant challenge for healthcare providers who are struggling to navigate the various testing options to determine what is in the best interest of their patients. The competitive commercial landscape and aggressive marketing of NIPT to both patients and providers can further confound clinical decision-making given the paucity of information available to providers that is not delivered with an angle aimed at selling the test.

NIPT Statistics in Marketing Materials

We have noted that multiple labs offering testing have promoted extraordinarily high positive predictive values (PPVs) in their marketing materials distributed over the past year and on their websites ^ and on laboratory test reports. These tables include information regarding PPV frequently reference data from the Illumina platform and VerifiTM methodology and a study by Futch et al. as the source.

 

Performance Data Presented in Marketing Brochures for NIPT
Condition PPV NPV Sensitivity Specificity
T21 0.994 0.999 >99.9% 99.8%
T18 0.910 0.999 97.4% 99.6%
T13 0.843 0.999 87.5% >99.9%

These figures (or slight variations thereof) have been observed in the marketing materials for multiple laboratories offering NIPT. These specific statistics were reproduced from an InformaSeq brochure and sample test reports available online

 

The PPVs reported in this table – being widely distributed on test reports and as educational information for providers – have NOT been demonstrated by the referenced study by Futch et al. or any published NIPT studies of which we are aware.

Of course, the PPV of a screening test depends on the prevalence of the condition in the population being screened. Using the sensitivity and specificity of testing accompanying these predictive value data in the same brochure, one could only derive PPV of >99% if the prevalence of Down syndrome in the screened population was 25% or 1 in 4 pregnancies, far higher than the a priori risk for the vast majority of women undergoing prenatal screening.

PPV = (sensitivity x prevalence) / ((sensitivity x prevalence) + (1 – specificity)(1 – prevalence))

.994 = (.999x.25)/((.999x.25) + (1-.998)(1-.25)

In contrast, if we utilize performance statistics provided by the laboratories, we calculate a PPV of 33% in a population with a prevalence of 1 in 1,000 (which is similar to the prevalence for women in their 20’s) and a PPV of 83% in a population with a prevalence of 1 in 100 (which is similar to the prevalence in women age 40).

The Futch Factor

The study by Futch and colleagues that is frequently cited in marketing materials for NIPT does not demonstrate the high PPVs that are referenced, although we suspect that these statistics were arrived at through a series of assumptions about the Futch data that we will attempt to outline.

This study reported that in a cohort of 5,974 pregnant women tested, there were 155 positive calls for T21, 66 positive calls for trisomy 18, and 19 positive calls for trisomy 13. In this published report, only a fraction of the positive NIPT results had confirmation of the fetal karyotype, 52/155 cases of Down syndrome (33.5%); 13/66 cases of trisomy 18 (19.7%); and 7/19 cases of trisomy 13 (53.8%). There was 1 case of Trisomy 21 that had a normal NIPT result (false negative result), however negative test results were not methodically followed-up, so the true false negative rate for the screened conditions is unknown.

In analyzing the data presented by Futch et al, for marketing materials to derive PPVs of >99% for Down syndrome, 91% for trisomy 18 and 84% for trisomy 13 would require that all of the positive calls WITHOUT follow-up by karyotype confirmation were true positives.

 

Outcomes data from Futch et al, 2013 and projected PPVs based on category inclusion or exclusion as true positive.
T21 T18 T13
NIPT Positive 155 66 19
Confirmed (karyotype or birth outcome) 52 13 7
Discordant (Unexplained NIPT results that do not match karyotype from a source or birth outcome) 1 6 3
No information (laboratory did not obtain any information on outcomes) 22 12 0
Pregnancy loss (miscarriage , demise or termination without karyotype) 7 5 2
Unconfirmed (no karyotype or birth outcome known but history of clinical findings suspicious of aneuploidy such as ultrasound findings or high-risk biochemical screening results ) 73 30 7
Total Positive NIPTs where follow-up karyotype not confirmed 102 47 9
High End PPV* 99.4 90.1 84.2
Low end PPV** 33.5 19.7 36.8

*High end PPV- It appears that marketing material PPVs are considering all categories, including confirmed, no information, pregnancy loss, and unconfirmed to be TRUE positives in determination of PPVs.

**Low end PPV- calculated considering all cases, which were not discordant to be false positive results. A minority of positive NIPT results were confirmed with birth outcome or fetal karyotype information.

 

Given that Futch et al. did not have confirmed fetal karyotype or birth outcome follow-up for the majority of positive calls, it seems at best unlikely, and at worst impossible, that all of these positive NIPT results were correctly called, rendering claims of such high PPVs in the marketing materials based on this assumption to be unfounded. On the other end of the spectrum, if the PPV was calculated to include the not-karyotyped/no-birth outcome information pregnancies as false positive, the assumed PPVs would be 33.5% for Down syndrome, 19.7% for trisomy 18 and 36.8% for trisomy 13. Since the study does not report follow-up karyotype for the majority of positive test results, the true PPV for these NIPTs test likely lies somewhere in-between the high end PPV and low end PPV, perhaps closer to the 40-45% (for T18 and T21) previously reported in another Illumina sponsored study.

While the PPV of NIPT for Down syndrome, trisomy 18 and trisomy 13 exceeds that of traditional biochemical screening, no studies have demonstrated test performance as high as those presented in many of the PPV/NPV tables that are being provided to healthcare providers in marketing materials and, in some cases, on test reports.

A Call For Truth In Advertising And In Test Reporting

Honest communication about test performance metrics must be available to providers so that they can provide accurate counseling to patients making critical decisions about their pregnancies. While most labs do state that NIPTs are screening tests and that confirmatory testing of positive results is recommended, it is not surprising that providers and patients are having difficulty appreciating the possibility of false positive results when the laboratories are incorrectly reporting positive predictive values that exceed 99%. The consequences of relying on lab-developed materials rather than a careful analysis of the available literature are significant. There are reports of patients terminating pregnancies based on NIPT results alone. It is not surprising that some women choose not to pursue diagnostic testing to confirm abnormal NIPT results given the very high stated predictive value.

It is imperative that we recognize not only the potential benefits of these new technologies but also their risks and limitations. Testing companies are primarily responsible to their shareholders and investors, so information provided by companies about their products is largely aimed at increasing test uptake. Professional societies need to call for independent data and federal funds need to be made available to support independent research related to NIPT. Policies and best practices cannot arise from the industry-influenced studies that are currently available. While some regulatory oversight of marketing materials will likely be necessary, we urge the laboratories to consider their marketing approach and how it is affecting patients and providers. If laboratories want to truly partner with patients and providers, they need to provide accurate and straight-forward information to limit provider liability and likewise, help patients avoid making life-changing decisions based on inaccurate and/or confusing information related to test performance. As a medical profession can we come together and make this change without regulatory oversight? Now that would be a medical breakthrough.

^ – Notably, Counsyl has also recently produced a table that provides more accurate estimates of their NIPT predictive values

 

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Guest Post: NIPS: Microdeletions, Macro Questions

by Katie Stoll

Katie Stoll is a genetic counselor in Washington State. She graduated from the Brandeis University training program in 2003 and since that time has held positions in the areas of prenatal, pediatric and cancer genetics. 

http://foter.com/search/instant/?q=question

At the recent National Society of Genetic Counselors Annual Education Conference in New Orleans, a presentation raised some important questions about noninvasive prenatal screening (NIPS). According to the speaker, a woman with a vanishing twin pregnancy underwent NIPS with an expanded microdeletion panel and the results showed findings “suggestive” of a chromosomal microdeletion syndrome.

The patient underwent amniocentesis with a SNP microarray and the results were normal. In a follow-up call with the NIPS lab, the genetic counselor learned that multiple copy number variants were observed (not originally reported) in the original sample. The lab suggested that these variants could be associated with a malignancy or fibroid tumor (and were of course unlikely to be associated with a microdeletion syndrome in the fetus).

As a result of this genetic counselor’s follow-up phone call and due diligence, the patient underwent an extensive work up for possible cancer, but no explanation was found. NIPS was repeated and this follow-up study was normal.

My first thought in hearing this case was – That poor woman! First a lost twin pregnancy, then concern for a severe condition in her baby, anxiety about the amnio, and worry that she may have Cancer. Although I am not a health economist, my second thought was – Holy Cow! How can our healthcare system afford all of the follow-up testing that may come downstream from these tests? NIPS is promoted as a test that will lessen the need for follow-up procedures such as amniocentesis, but will that remain true as the list of screened conditions increases?

In October 2013 Sequenom expanded their NIPS test to include screening for microdeletion syndromes and Natera followed suit in Spring 2014. Some new companies entering the NIPS market are also advertising screening for microdeletion syndromes.

The addition of microdeletions is a brilliant business strategy for expanding the testing market to include all pregnant women. Even though microdeletions are rare, their incidence—unlike that of Down syndrome –is not linked to maternal age. Women who are currently not offered NIPS because they are not included in the high-risk categories proposed by the American College of Obstetricians and Gynecologists (ACOG) guidelines could now be given a reason to undergo NIPS—even though the predictive ability of the NIPS for rare conditions is less than impressive.

Women who elect the test because of an interest in Down syndrome or because they are eager to learn fetal gender may unknowingly be screened for rare microdeletion syndromes which they know little to nothing about. To add to the complexity, a maternal microdeletion condition may be an incidental finding. In a poster presented at the NSGC meeting this year, Sequenom presented a series of 22q11 deletions detected with their MaterniT21 PLUS test. Included in this report were two mothers who were themselves incidentally diagnosed with 22q11 deletion syndrome. Based on the consent form on the Sequenom website it seems unlikely that these women had any idea such a result may occur.

Where is the evidence to support this expanded screening?

These tests are being performed despite there being no published clinical validation studies. There have been some case reports and proof of concept studies; however given that this testing has been commercially available for over a year now, there is shockingly little published about cell free DNA screening for microdeletions. An abstract from a poster presentation at the ACOG annual meeting in April 2014 evaluated 6 samples (or is it 7? – it is not clear from the abstract) from pregnancies known to be affected with microdeletions and 8 simulated samples. They conclude, “This is the most comprehensive, accurate validation of noninvasive microdeletion detection hitherto… This approach will enable accurate, noninvasive, prenatal population screening for these severe disorders.”

Proof of concept is one thing; proof of clinical validity is another. If we value evidence-based medicine, a sample of six (or seven) affected pregnancies is a long way from being a basis for population screening. Whether population-wide screening for extremely rare disorders is worth paying for is, of course, a question in itself.

But in the unregulated environment of laboratory-developed tests, we adopt first and report out results later. Accompanying this process is a lack of transparency – labs performing NIPS with microdeletions have not made performance statistics publicly available and thus patients and providers have no way of determining the accuracy of microdeletion NIPS. In a webinar hosted by Sequenom , the presenters were asked about the positive predictive value (PPV) of Sequenom’s screen for microdeletions. One speaker replied, “We have calculated them. However, what we would like is essentially to wait a little bit to give you more clinically relevant results. Because so much depends on the fetal fraction of the sample and so on and so forth, so we feel that the more appropriate number to release is after we have done 50,000 samples, how many have we found, how many have we reported back, how many were confirmed, how many were in line with the clinical picture.”

Shouldn’t the accuracy of the test be publicly known before it is run clinically on 50,000 women?

Labs have given us only a glimpse of their performance statistics. I was previously provided information from Natera regarding estimated PPVs for the microdeletions on their panel, but I cannot locate this information anywhere in the public forum. The table I was provided stated a 1/19 PPV (5.3%) for 22q11 with a Fetal Fraction >6% and dropping much lower (to 1/45) with decreased fetal fraction (interesting thread here of multiple women with a 1/19 chance of 22q11 on their NIPS result).

In a letter to the editor, former CMO of Sequenom Allan Bombard and colleagues reported that they had evaluated 264 samples from pregnancies with known microdeletion and microduplications or “enriched genomic mixtures” and report a 100% sensitivity and 99.3% specificity. Applying these statistics to 22q11.2 deletion syndrome (the most common microdeletion syndrome on the panel with an incidence of 1 in 4,000) indicates a PPV of about 0.036 or 3.6% . The overall PPV would be expected to be lower given the very low incidence of the other microdeletions on the panel. At the NSGC meeting this year, Sequenom presented some preliminary data from a series of 120,726 samples screened from October 2013 – July 2014 with test performance that exceeds those estimates. Although they did not have complete follow-up data for positive and negative results, a press release from the company following the NSGC meeting reports “high positive predictive values (estimated combined PPV ranged from 62% to 94%)”.

The limited information available suggests PPVs for microdeletion syndromes fall within a broad range of <3% – >90%. Published peer-reviewed studies are needed to help clarify the PPV associated with this testing so that healthcare providers and patients can make informed decisions about utilizing and interpreting this testing.

About a year and a half ago I published a piece on the DNA Exchange that discussed the importance of PPV in interpreting NIPS results. This was written for an audience of genetic counselors, but the posting is being increasingly used as a venue for patients to share their stories and seek information about their test results. Many patients report considerable anxiety – “the waiting is killing us…we have been devastated for the better part of 3 weeks now” – and some express regret for undergoing this testing at all, “I too wish I would of just done the typical old fashion test so nothing was in the back of my mind and hours of my life would be given back…” Recently, a woman remarked that she did not consent to additional testing for microdeletions and indicates her frustration with not being able to find information about the PPV for this test, “Not only are they essentially experimenting on us…they are not transparent about the potential problems with validity or low PPV.”

As genetic counselors, we are implicated in these companies’ approach. We should be demanding better evidence before leading our patients towards testing that could create this kind of distress. We need to be asking good questions, and we should demand good answers. If we cannot figure out how reliable a screening test is from a thorough review of the literature, I think we really need to ask ourselves if we should be offering it in a clinical setting.

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NIPS SPIN

Advertising is the art of making whole lies out of half truths. ~Edgar A. Shoaff

Every few years a new screening technology comes zooming down the prenatal pike, sometimes arriving more quickly than we might like. First there was maternal age, with the magical age of 35 as the cut-off. Low maternal serum AFP arrived in the 1980s and the OB community embraced it virtually overnight when ACOG’s Committee on Professional Liability issued a statement that practitioners could be held legally liable if they had not offered this screen to a patient who had given birth to a child with Down syndrome. This was followed in short order by the Triple Screen, The Quad Screen, nuchal thickening, Integrated Screening, etc., each one a statistical notch above its predecessor. The latest iteration – cell-free fetal DNA or Non-Invasive Prenatal Screening (NIPS)  – stands head and shoulders above the rest. Two of our colleagues have already discussed the limitations and strengths of NIPS here on The DNA Exchange.*

NIPS is big, as in global big. One lab makes its brochure available in more 20 languages, from Afrikaans to Xhosa (the pregnancy gods must be crazy, dropping pamphlets out of The Cloud). Tens of millions of women around the world are likely to undergo NIPS in the near future. And pregnant women are a “renewable resource” –  a whole new batch pops up every day and many women will have two, three, or more children. Competition for market share among labs is stiff and there is little incentive to dissuade women from undergoing prenatal screening. It’s not that labs coerce women to undergo screening, advocate eugenic agendas, or run roughshod over personal autonomy. All labs would support a woman’s right to decline prenatal screening and Lord knows they stay away from the abortion discussion. But if enough women decline, then there is no incentive to offer the screen. The companies have something to sell and will spin their product to attract customers.

Which brings me to the subtly misleading implications of the name Non-Invasive Prenatal Screening. Sure, NIPS is non-invasive. But so is ultrasound, AFP, HCG, etc. All of these screening tests are non-invasive and therefore do not carry a direct risk of fetal loss. NIPS  is no different from the rest in that sense. It is superior to other screens in terms of having a very low first positive rates, high positive predictive value, and high sensitivity. But NIPS is still an alternative to other screening tests, not to amniocentesis or CVS.

Yet the websites of companies that offer NIPS communicate a different message that subtly suggests that NIPS is in fact an alternative to amniocentesis/CVS instead of an alternative to, say, the Integrated Screen:

First we thought the PC was a calculator. Then we found out how to turn numbers into letters with ASCII – and we thought it was a typewriter. Then we discovered graphics, and we thought it was a television. With the World Wide Web, we’ve realized it’s a brochure. ~Douglas Adams

The suggestion that NIPS is a diagnostic test is further reinforced by reassuring text in large, appealing fonts – Comprehensive, Accurate, Trustworthy, and, my personal favorite, No Confusion. Such wording conflates screening tests with diagnostic tests. Who could resist a test that boasts to be >99% accurate, especially when combined with images of smiling, beautiful parents and babies so cute that you wish your touch screen would allow you to hug them? It is easy to see why parents might be confused and some genetic counselors feel that 75% of their patients may think that NIPS is diagnostic. Yes, the labs also offer comparison to other screens, information about the conditions being screened for, links to disability focused websites, and acknowledge the role of diagnostic testing. But information does not sell products; images and impressions do.

http://en.wikipedia.org/wiki/The_Treachery_of_Images

The Treachery of Images by René Magritte

NIPS is a pretty good screening tool that can help patients decide if they want to proceed to diagnostic testing such as amniocentesis or CVS. However, the first step in the process of considering any testing should be a soul-searching and difficult discussion between parents and with their care providers about views on disability, parenthood, expectations for their children, and beliefs about pregnancy termination (I can’t prove it, but I am pretty sure that discussion is not taking place anywhere near as frequently as it should). For parents who feel it is important to know the chromosomal status of their baby, the next step is to outline the pros and cons of screening tests, emphasizing that a screen only provides a probability that a child may have a particular chromosomal disorder. The risk estimate provided by the screening test may help parents decide if they wish to undergo diagnostic testing.

One might counter that labs are commercial entities engaging in good old American advertising, which everybody knows is not exactly a strictly honest business. But prenatal screening is not like trying to sell Coke vs. Pepsi or Ford vs. Toyota or Chia Pet vs., well, whatever it is that Chia Pets are in competition with. We are talking about babies, our deepest hopes and dreams, and the core values that define our humanity. This demands a higher standard and this is where genetic counselors need to work with their laboratory employers to elevate the discussion.

 


* Missing from much of the professional  discussion about NIPS has been the viewpoint of people with disabilities, their families, and their advocates. As Rachel Adams points out, the Down syndrome community in particular might feel particularly targeted by a test named Maternit21 – but that thorny topic is for another day.

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Guest Post: NIPS: A Call to Embrace and Educate!

By Lisa Demers

Lisa Demers is a certified genetic counselor working in a prenatal diagnosis program at Dartmouth-Hitchcock in Nashua, NH.  She graduated from the Arcadia Genetic Counseling Program in 2003.  Lisa has been president of the New England Regional Genetics Group, is a member of the New Hampshire Perinatal Loss Taskforce, and is the proud mother of two little boys who teach her more and more about Star Wars every day. 

I feel like it’s time to show some appreciation for the amazing screening test that has truly enhanced the prenatal screening world.  Non-invasive prenatal screening (NIPS) has taken our prenatal world by storm and is rapidly infiltrating university hospitals and private practices alike.  This is a change (who really likes change?) and it’s fast.   Testing has jumped out of the controlled hands of research laboratory scientists and into the lucrative playing field of investor-backed industry.  But is this a bad thing?

NIPS has taken traditional screening and made it better.  There is no denying that NIPS is a superior screening test.  The benefit of NIPS over traditional screening is acknowledged by the rapid approval of coverage by major insurance plans. I applaud Katie Stoll in her eloquent summary of the discrepant positive predictive value (PPV), but I do not think this area of ambiguity should overshadow the benefits of testing.  The PPV for a “high risk” (or whatever language the report contains) sample, even if it is 11% (using the data in Katie’s initial post), is about the same as a 1 in 9 risk for trisomy 18 using traditional methods.   So is the counseling really very different?   “This screening test suggests a very high risk for trisomy 18, diagnostic testing will tell us for sure”.

Our knowledge about how to best utilize this test and interpret the results is an ongoing process.  This is completely on par with other technologies. At one point, supernumary rings were identified on karyotype with little way to identify the origin.  The argument that we shouldn’t use a technology until we completely understand it is unreasonable.  We need large testing numbers to give us these uncertain results so that we can learn from them.  Ambiguity with test results is hardly a new concept for us.  Genetic counselors deal with this all the time!  Our counseling isn’t really changing; it’s just the same uncertainty coming from a different test.

I argue that this test provides much LESS ambiguity since most women are getting reassuring results.  The number of women who are screen positive is dramatically decreased.   Fewer women being anxious, fewer amnios being considered and performed, and fewer losses of otherwise normal babies.    And why wouldn’t an informed patient want the BEST screening test?   And why wouldn’t providers want to offer it?

I absolutely acknowledge that not all patients are fully informed about NIPS prior to testing, and I hate to think about the ignorance that providers may pass along to patients.  But what genetic counselor hasn’t had a patient arrive at their office with an abnormal screening result thinking that their baby is, in fact, affected?  We hear this endlessly.  And how long has traditional screening been around?  And those results even have a risk estimate listed!  Sometimes I like being the hero in these situations “You mean my pregnancy is at a one percent risk for Down syndrome?  What a relief!”  The misinterpretation of testing results is inevitable.  We should not back away from better testing simply because some people do not understand.

While I agree that I would prefer that the commercial labs present their results with some more obvious notation of the limitations of the testing, no report can eliminate ignorance.  So perhaps our focus can be a shift to better education.  After all, isn’t that we do?  We need to talk with providers in our area and help them understand the test more clearly.  Review with the nursing staff when a referral is sent to us that the results are screening and not diagnostic.  I can tell you that in my own experience, education isn’t always successful because I still have providers who offer universal SMA and Fragile X testing without being able to interpret the results. *Sigh*  But these patients are ultimately referred for counseling, and I consider that a success.

Education at the patient level is important too.  Group counseling sessions can be an effective way to inform the pregnant population, especially about universal topics like screening.  The overwhelming task of education is not unique to prenatal genetic counselors, but to the profession as a whole.  Rather than hold back on a test that is truly superior because providers misunderstand it, why don’t we try to tackle the larger issue of provider education?

What I hope is that the consumers of NIPS can work closely with the industry providers to further study the performance of this technology to better understand cell free fetal DNA and its utility in pregnancy screening.  Let’s work together in educating providers about the testing and the importance of pre-test counseling.  Patients deserve it.  Without the cooperation and participation from genetic counselors we risk delaying universal acceptance of NIPS.  Let’s all jump aboard and steer this train.

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Guest Post: NIPS And The Threat To Informed Decision Making

by Katie Stoll

Katie Stoll is a genetic counselor in Washington State. She graduated from the Brandeis University training program in 2003 and since that time has held positions in the areas of prenatal, pediatric and cancer genetic counseling.

A few months ago, I reached out to the DNA Exchange readership and called for more truth in advertising by the Noninvasive Prenatal Screening companies regarding the accuracy of test results. I recently returned from the National Society of Genetic Counselors meeting where I had the opportunity to survey the marketing and patient materials from labs offering NIPS and to learn about the experiences of my fellow genetic counselors with these new tests.

Not surprisingly, in this dynamic and rapidly evolving field, all of the companies have updated their materials. Some brochures proudly acknowledge how quickly this testing is being integrated into clinical use. It feels like we are being patted on the back for adopting this new test quickly and without question.

I remain very concerned about the misleading claims in the marketing materials aimed at providers and in the patient directed brochures. It is easy to see how the language of the brochures could lead healthcare providers and patients to conclude that these tests are diagnostic or near-diagnostic. These quotes from the materials illustrate my point:

“Definite, informative results.”

“Positive or negative results.  Never maybe.”

“No confusion.  Just simple, clear results.”

To my knowledge, there are no new large studies to dispel my concerns about the positive predictive value of NIPS. Depending on the prior probability, a significant portion of positive results may be false positives– especially with rarer conditions such as Trisomy 18 and Trisomy 13. And because these technologies have been rapidly integrated into clinical practice based on limited research, we do not have robust outcome data to see how false positive and false negative data are playing out in clinical practice.

Since most NIPS testing is done outside of a clinical research protocol, the labs that choose to put resources into follow-up are at the mercy of the providers to share that outcomes information.  Even in the best scenarios, voluntarily reported outcome data are not likely to tell the whole story. I spoke with a testing company representative regarding a poster presented at ACMG last year which based its false positive and false negative results on ad hoc feedback. When I inquired about the meaning of ad hoc feedback, it was explained to me that the company didn’t have the resources to track outcomes so were relying on providers to let them know if the testing results were incorrect. Of course, if a patient terminates her pregnancy based on a false positive test result, nobody will know that the NIPS result was incorrect.

Don’t think a patient would terminate based on NIPS alone? We all hope that women who receive adequate counseling about the limitations of the testing would confirm results with a diagnostic test, but this is not always the case. At a presentation during the recent NSGC Annual Education Conference, one lab referenced preliminary data showing some patients are terminating pregnancies without first getting diagnostic testing, and in the absence of ultrasound findings. While this tracking has some limitations, this lab should be applauded for investing resources in tracking outcomes data and for sharing these data with genetic counselors. Hopefully we will see it published soon and other labs will follow suit.

This situation of patients making reproductive decisions based only on NIPS results may be particularly problematic in communities that don’t have ready access to genetic counseling and/or maternal fetal medicine services.

Imagine this scenario:  a 35-year-old woman living in small town, USA who has limited access to abortion services beyond the first trimester, receives a positive result for Trisomy 13. Based on positive predictive values calculations, there is an 8% chance that her “positive” result is a true positive. But, the patient – and her doctor – may think the probability is much higher, maybe even close to 100%, based on the reporting practices of the labs, which may say “Aneuploidy detected” or “Positive” for Trisomy 13. This does not support informed reproductive decisions.

This patient has 3 options:

  1.  Wait for an appointment at a high risk referral center, at some distance from her home to undergo diagnostic testing. This may limit her reproductive options by delaying time to diagnosis (the later a pregnancy termination occurs, the more expensive it is, and pregnancy termination outside of the first trimester is often not available in many smaller communities).
  2. Seek out pregnancy termination options in her local community based on the NIPS results alone – knowing that she is up against a gestational age ticking clock.
  3. Decline further testing and continue the pregnancy.

If the patient feels that she would not want to continue a pregnancy given a Trisomy 13 diagnosis, and she understands the limitations of the testing, I would imagine that she likely would feel it was worth the wait and the travel for diagnostic testing. However, given the emphasis on the accuracy of NIPS based on the lab reports, and the misconception by OB providers that this testing is “nearly diagnostic”, it is easy to imagine a scenario where she may elect to have a termination based on NIPS alone.

Based on an aggregate of data from the NIPS companies from the first quarter of 2013, one health economist estimates that NIPS is utilized by 40% of the high-risk population in the US, and this number is growing rapidly. So while the patients you see in your genetic counseling practice may be very informed about the limitations of the testing given your expert counsel, this statistic suggests that most NIPS is probably taking place outside of our offices.

We must continue the conversation about how NIPS is marketed and used in prenatal care. While the advantages to a more sensitive screening test are obvious (e.g. fewer women needing to undergo diagnostic testing), we must recognize the largely undisclosed limitations and dangers. Without adequate counseling, patients are being harmed by the misleading claims about the accuracy

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Guest Post: NIPS Is Not Diagnostic – Convincing Our Patients And Convincing Ourselves

By Katie Stoll, MS

Katie Stoll is a genetic counselor in Washington State. She graduated from the Brandeis University training program in 2003 and since that time has held positions in the areas of prenatal, pediatric and cancer genetics.

A couple of years ago we were just beginning to learn about a new prenatal testing technology termed Noninvasive Prenatal Diagnosis. It was soon relabeled as Noninvasive Prenatal Testing, and now the American College of Medical Genetics and Genomics recommends this be taken one step further by terming it Noninvasive Prenatal Screening (NIPS) to highlight the limitations of this new technology.

As currently reported by labs, NIPS presents new challenges for genetic counselors. Of particular importance is figuring out how to convey to patients and healthcare providers why relying on sensitivity and specificity alone may lead to misinterpreted results. In the absence of positive and negative predictive values there may be a tendency to assume that the high sensitivity and specificity reported with NIPS means that these tests are more powerful – more diagnostic – than they actually are.  

It is imperative that we understand both what the terms mean and how they relate to a person’s likelihood of having a condition.   Sensitivity measures the true positive rate – the proportion of actual positives which are correctly identified as such (e.g., the percentage of fetuses with Down syndrome (DS) who have a positive test result). Specificity measures the true negative rate – the proportion of actual negatives which are correctly identified as such (e.g., the percentage of fetuses who do not have Down syndrome who have a negative NIPS result for DS).

A test can have both a high sensitivity and specificity without being a good predictor of whether the condition is actually present. The likelihood that a positive test is a true positive result also depends on the incidence of the condition.

Sensitivity Graph

Genetic counselors are used to thinking about aneuploidy screening in terms of PPV, as this is generally the format for reporting maternal analyte screening such as Integrated , Quad screens, etc. Analyte screening takes into account the prior probability based on maternal age and provides a PPV as the end result. For instance, an analyte screen result may be reported as Positive with a 1 in 50 chance of Down syndrome. The PPV with analyte screening lets us know how many patients with a “positive” test will actually have a pregnancy affected with the condition and reporting results this way makes it clear that this is a screening test.

Can we apply the same interpretation to NIPS results?  Some labs provide a “risk score” which appears similar to what we see with analyte screening, but I am told by the labs that the vast majority will be reported as either >99% chance or <.01% chance.  Some labs do not report a risk score, instead giving essentially a positive or negative result. But does this mean that greater than 99% of women who receive a >99% or a positive result are actually carrying a fetus with Down syndrome or other chromosome condition?

Given that women 35 year and older are a population targeted for NIPS let me work out the expected NIPS results given the approximate sensitivities and specificities reported for a hypothetical population of 100,000 thirty-five-year old women (while I cannot tell you the specific number of women age 35 who give birth per year, CDC data suggests that for the past several years about 400,000 – 500,000 women in the age 35-39 have given birth each year in the United States – so 100,00 births annually by 35-year-old mothers is probably in the ball park of the national trend.

The performance data vary significantly from lab to lab – for the purpose of this illustration, I am using sensitivity and specificity in the range of what has been reported.  The data below are based on the chance of Trisomy 21, 18 and 13 at the time of amniocentesis for a woman 35 at time of EDD1.

Down Syndrome

Trisomy 18

Trisomy 13

Incidence

1/250

1 / 2000

1 / 5000

Affected Fetuses

400

50

20

Sensitivity

99.5%

98.0%

90.0%

Specificity

99.9%

99.6%

99.8%

Total test positives

498

449

218

True test positives

398

49

18

False positives

100

400

200

Positive Predictive Value

80%

11%

8%

If we add all of the positive results together in a population of 100,000 thirty-five-year old women we see that 1165 (1.2%) have positive test results for Trisomy 21, Trisomy 18 or Trisomy 13.  Note, though, that only 465 of these results will be true positives. This indicates that the majority of the time (greater than 60% using these statistics), a positive result on NIPS for a 35-year-old woman will be a false positive – and this doesn’t even include calculations for sex chromosome aneuploidy which some NIPS labs also screen for.

Notably, the negative predictive value for NIPS is very high indicating that a negative test result is a true negative >99% of the time. But how do we reconcile that for many women, the chance of a false positive with NIPS may be higher than the chance of a true positive result when that seems to be contradicted by way the labs are reporting the results? 

In trying to explain the chance of a false positive result to patients with a “positive” test report in hand, I have found that I am met with disbelief. I can understand why – if a test says there is a>99% chance of Down syndrome and the lab says the test has >99% sensitivity and >99% specificity, how could this test be wrong?

While genetic counselors understand the limitations, the reporting practices of the labs place us in a position in which we have to work hard to convince our patients that NIPS is only a screening test.

Currently four labs offer NIPS in the U.S. and all have different strengths and weaknesses in their reporting practices. All could be improved by making the limitations of this technology more obvious.  In some cases the language used in the reports gives the appearance that NIPS is diagnostic. For example, one company’s report suggests that the healthcare provider should advise for “additional diagnostic testing”.  The labs vary in whether the need for genetic counseling following a positive result is recommended.  Additionally there is variability in the transparency of how the performance data are derived.

Given that the performance statistics vary significantly, we need to be sure to take these details into account when considering PPV. I  encourage genetic counselors and other healthcare providers to critically look at how the performance data are derived.  The sample sizes on which these numbers are based are often quite small and the confidence intervals can be broad.  I was surprised to see in the fine print of one report that the performance data “excludes cases with evidence of fetal and/or placental mosaicism.” Given that mosaicism is a known cause of false positive results and because mosaicism cannot be definitively determined through NIPS, it doesn’t seem accurate that these cases should be excluded from calculations of test performance.

The pitfalls of interpreting NIPS results is a challenge we need to address because NIPS is increasingly taking place without the involvement of genetic counselors in pretest or post-test counseling. There is real concern that patients are making pregnancy decisions based on screening tests with the misunderstanding that NIPS is diagnostic. 

I write this as call to the NIPS labs to change their reporting practices to better emphasize the screening nature of this technology. Providing some positive predictive value estimates would be tremendously helpful as we try to make sense of NIPS results for our patients. While it may be difficult to provide individualized risk assessment, a general table of how prior probability impacts individual test performance would be beneficial for interpretation. Furthermore, eliminating language from the reports that suggests these tests are diagnostic and giving more transparency to ways in which performance data are calculated would also be welcome changes.

As genetic counselors, we strive to ensure informed decision-making for the clients we see. Key to informed decision-making is an understanding of the limitations of this evolving technology. As fellow patient advocates, I hope the genetic counseling community will join me in requesting increased accountability and responsible reporting on the part of the labs regarding NIPS.

I would like to acknowledge Evan Stoll, retired GAO data analyst for his contributions to this piece.

Please Note: Authors who contribute to The DNA Exchange cannot offer medical advice. Many commenters have raised interesting and thoughtful questions about NIPS. If you have undergone NIPS and have questions, you should meet with a certified genetic counselor. To locate a genetic counselor, go to the  Find A Genetic Counselor section of  the website of  The National Society of Genetic Counselors.

  1. Hook EB. Prevalence, risks and recurrence. In: Brock DJH, Rodeck CH, Ferguson-Smith MA, editors. Prenatal Diagnosis and Screening. Edinburgh: Churchill Livingston, 1992.

 

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