By Susan Dammann, RN, LAS, Medical Specialist
Reporting in Prenatal Tests: What Patients Should Know published in Medscape News and WebMD, Kathleen Doheny described a recent investigation revealing there are significant inaccuracies in non-invasive prenatal screening and that some women and doctors are misinterpreting the positive results from the new generation of prenatal tests including MaterniT21Plus, Verifi, Panorama and Harmony. In some instances, women are terminating their pregnancies because of it. This decision appears to be based on the screen alone without obtaining tests to confirm a negative diagnosis.
Beth Daley from the New England Center for Investigative Reporting in an excellent article Overused and Misunderstood stated "a three-month examination by the New England Center for Investigative Reporting has found that companies are overselling the accuracy of their tests and doing little to educate expecting parents or their doctors about the significant risks of false alarms."
"All claim to offer expectant parents the chance to know with almost 100% accuracy, and as early as 10 weeks into a pregnancy, the likelihood that the developing baby has any genetic abnormalities such as Down syndrome, Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13), or a few other chromosomal anomalies" writes Nora Sullivan with the Charlotte Lozier Institute in her article Non-invasive Prenatal Screening Expands Disability Discrimination Abortion.
Daley goes on to say: "A screen is a test given to a general healthy population and usually has high sensitivity so that any possible problems are flagged. Because of the high sensitivity, false positives are more common. Also, screens are not necessarily approved by the FDA. Because of a loophole from the 1970's, these types of screening tests are not subject to the same regulation as other medical devices or procedures. A screen is always supposed to be confirmed with a diagnostic test. A diagnostic test is designed with high specificity for a particular condition flagged by the screen. It is often more invasive and is meant as a tool to make a definitive diagnosis."
The problem appears to be not understanding a "statistical blip" in how the test results are reported or what is called "positive predictive value". What is critical for both health care providers and patients to understand is that the test is a "risk-based test" not a diagnostic test and a positive test result is only indicative that they have a higher risk of having that particular issue. The article reported that in the general population of women, a well-regarded study published in the New England Journal of Medicine showed that the test was correct for only about 40% of women who tested positive for Edwards syndrome (trisomy 18).
Daley said, "If companies are presenting these screens to be as good or better than a diagnostic test, doctors believe them and parents are aborting as a result, then the companies are seriously negligent."
Therefore if a patient comes into a pregnancy center considering abortion if/because test results come back positive, it is important to educate the patient that this test is only a screening for risk. A positive result is only an indication that their risk may be higher, but the test result could be wrong and a confirmatory test like a CVS (chorionic villus sampling) or an amniocentesis is needed to be sure. A patient should always get a confirmation with an FDA approved diagnostic test.
Aborting a child due to a genetic abnormality is disability discrimination. Prenatal tests should never be used for such purposes. When a disability is discovered rather than termination, options for the provision of treatment or hospice care should be offered.
Armed with the information above, we can help women who may be determined to abort due to a negative diagnosis to get further testing for verification. This will facilitate additional time to help them with alternative options should the diagnosis be positive.
