This thoroughly reported and carefully written story avoids giving pregnant women false hope of an easier way to detect genetic anomalies while still presenting some compelling information about a new blood test.
Pregnancy can be anxiety inducing because of the sheer number of tests already required of women: frequent blood tests, ultrasounds, and amniocentesis in many cases. Add to that the barrage of stories about the way diet and environmental conditions may be affecting in utero development at any given point and one can understand why women might want a simpler solution to find out whether their child might have a genetic disorder. Overall, we think if more stories approached screening the way this story did there would be fewer people demanding the latest over-hyped test from their doctor.
This is a “hope for the future” level test that may be inching its way to market. It’s not available now and won’t be in the immediate future – and the story makes that clear.
We’ll give the story the benefit of the doubt for again leaning on an independent expert who says the technology is likely prohibitively expensive. While no dollar estimate is given, we think this is good enough for now.
As with the harms, the story does quantify the benefits in one way. It says, “It could help avoid up to 98% of these screening procedures, according to the study, which appears in BMJ.” It also says, “The new study included 753 pregnant women who were at high risk for having a child with Down syndrome. Of these, 86 women were determined to be pregnant with a child with Down syndrome.”
The story does quantify potential harms in one way by noting, “There were no false-negative results with the new test.” We wish the story also spoke about false positives. False positives are certainly part of the stress and harms from any screening test that need to be considered. In this case, it appears the false positives were low but not negligible.
The story adequately describes the study design.
The story does avoid disease monitoring, but we wish it had included some of the data from the paper about the frequency of Down syndrome and even some of the other disorders. The LA Times blog piece managed to do this in much less space.
The story provides a wealth of outside experts who provide great commentary and context about the study’s findings. We wish more stories about screenings had quotes like these: “In a year or two, this test may be available, but it won’t replace existing technologies, it will nudge its way into our armamentarium of available methodologies,” says Mark I. Evans, MD, director of Comprehensive Genetics in New York City, and an obstetrician/gynecologist at Mount Sinai School of Medicine, also in New York City. “The bad news is that prenatal diagnosis is not just about Down syndrome…Down syndrome represents about 50% of what we find, and this new test can help with that, but it may also give women a false sense of reassurance.”
The story tries to do a good thing by explaining at the very end that the new test is not a diagnostic test, as amniocentesis and chorionic villus sampling are. Rather, it’s a screening test. The distinction – and the significance of that – could have been made more clearly, but we give the story the benefit of the doubt.
The story leans on an independent expert to say that the test is “not ready for prime time….in a year or two, this test may be available.”
The story does not establish the test’s novelty, and this is largely because it does not provide the proper context. The study itself says, “In the past 20 years maternal age has been combined with ultrasonographic examination of the fetus and biochemical measurement of various proteins or hormones in the maternal circulation to improve identification of high risk pregnancies. This combined approach of screening can now identify more than 90% of affected fetuses, but there is still a need for invasive testing in 3–5% of the population.” This means that as many as 95% of all women would not need invasive testing to begin with, so this test is only potentially a breakthrough for a small minority of women. BMJ actually makes the novelty question easy to answer by breaking it down this way: What is already known on this topic: Non-invasive prenatal detection of fetal trisomy 21 is achievable by massively parallel sequencing of maternal plasma DNA Its diagnostic performance and practical feasibility in the clinical setting has not been tested on a large scale. What this study adds: Among high risk pregnancies clinically indicated for invasive prenatal diagnosis, non-invasive detection of fetal trisomy 21 can be achieved with the use of multiplexed massively parallel sequencing of maternal plasma DNA at 100% sensitivity and 97.9% specificity, giving a 96.6% positive predictive value and 100% negative predictive value. The sequencing test could be used to rule out trisomy 21 among high risk pregnancies before proceeding to invasive diagnostic testing to reduce the number of cases requiring amniocentesis or chorionic villus sampling.”
The story does not rely on a news release.