A Better Blood Test For Down's Syndrome?

Presently, moms-to-be are offered prenatal screening for a third chromosome number 21 by either blood tests, ultrasound, or a combination of the two. Recently, a newer blood test was cleared for use in women at higher risk - eg. older women or those with abnormal ultrasound findings. The use of this test, involving examining the cell-free dna in mom's circulation, for women at lower risk is still considered investigational. As such, the test, called Noninvasive Prenatal Testing or NIPT, in low risk women is not recommended by specialty societies and not covered by insurance plans.

Yesterday's publication by Drs. Diana Bianchi, Rajeevi Madankumar and many other investigators in the New England Journal of Medicine brings this test one step closer to more widespread usage.

In conclusion. our head-to-head comparison showed that noninvasive prenatal cfDNA testing performed better than standard screening methods, with an improvement by a factor of 10 in the positive predictive value for trisomy 21 in our predominantly low-risk patient population. The major advantage of using cfDNA testing was the reduction in rates of false positive results. A consideration of cost-effective ways to incorporate cfDNA testing into general obstetrical practice26 is beyond the scope of this study. Our findings, however, suggest that cfDNA testing merits serious consideration as a primary screening method for fetal autosomal aneuploidy.

It is still far to early to recommend widespread introduction of this test. The study was not meant to be a head to head comparison of present screening practice vs NIPT. The test was less predictive in one major chromosome syndrome other than Down's. Nevertheless, NIPT's lower false positive rate would mean fewer anxious moments, fewer invasive procedures, and fewer losses of normal wanted babies.

Faster, please.

Should Ultrasound Replace The Bimanual Pelvic Exam?

For complete disclosure, let me point out that my practice is limited to consultative ultrasound, having ceased the practice of clinical gynecology in 1986. When I trained at Bellevue in the late 1970's, even asking such a question would have outted you as a heretic punishable by intense re-education. But medicine swings like a pendulum do and today, this is a fair question. What's changed? The dual developments of portable real-time ultrasound followed by the vaginal transducer have swung that pendulum toward the imaging side. While sonograms have been thought of as the stethoscope for the obstetrician, the vaginal probe has greatly facilitated the pelvic exam. Further, there is now accumulated evidence to highlight the superiority of sonography to evaluate the female pelvis. One eye-opening study was by Padilla et al in 2000, assessing the predictive value of pelvic exam under anesthesia. Conclusion?

Bimanual pelvic examination has marked limitations for evaluating adnexa, even with ideal circumstances. Experience during postgraduate training in gynecology did not seem to improve examination accuracy. Patient characteristics such as obesity, uterine size, and abdominal scars limit the accurate palpation of the adnexa.

Now one reason why the pelvic exam is decidedly unpopular with patients is that, setting aside its invasiveness, it's uncomfortable. The more discomfort felt results in more patient's tensing the abdomen, causing the examiner to press harder and causing more discomfort. In this particular study, anesthesia removed the pain - pressure cycle from the equation and still found the bimanual examination lacking.

So how would ultrasound stack up? Tayal et al conducted a study of emergency patients who were being evaluated for pain. Patients underwent both a transvaginal sonogram and the clinical pelvic examination. The order of examinations was randomized. The group found the sonographic pelvic exam superior to the digital pelvic exam across all BMI classes. And remember, these were patients already in pain.

Similarly, sonography has been shown to be superior to bimanual exam in assessing gestational age in the first trimester and facilitating the management of inflammatory disease. In the assessment of uterine fibroids, an experienced examiner fared as well as sonography except in obese patients. As more and more Americans are dealing with obesity, the pendulum here again favors sonography.

My colleague from NYU Dr. Steven R. Goldstein suggested incorporating endovaginal sonography into routine gynecologic examinations. That time is long overdue.

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