Adding Ultrasound Ups Sensitivity of AFP Screen to 98%: Study


ORLANDO — Adding ultrasound to maternal serum AFP screening may help clinicians identify fetal neural tube defects, according to research that was presented during the annual meeting of the American Institute of Ultrasound in Medicine.

“From the standpoint of neural tube defect detection, the maternal serum AFP screening test remains a good test —in our series, more neural tube defects were detected if the test was used than if it was not used—but the sensitivity of the test is significantly better if gestational age is confirmed with ultrasound,” explained Jodi S. Dashe, M.D., of the University of Texas Southwestern Medical Center, Dallas.

“We were also pleased to find that in this series, the detection of neural tube defects with standard ultrasound was excellent,” Dr. Dashe added during the meeting.

Dr. Dashe and her associates conducted a retrospective study at their center to examine the role of ultrasound along with AFP screening for neural tube defects. For this investigation, they reviewed prenatal and neonatal datasets to find pregnancies that were complicated by neural tube defects.

Following their standard protocol, Dr. Dashe's team offered AFP screening between 15 and 21 weeks of gestation and performed specialized ultrasound for patients with an AFP of at least 2.50 multiples of the median (MOM).

For patients with an AFP of 2.00–2.49 MOM, standard ultrasound was performed.

Investigators identified 68 singletons with neural tube defects, 60 of which were identified prenatally.

Clinicians performed AFP screening in 33 study patients. An AFP elevation of at least 2.50 MOM occurred in 22 patients (67% sensitivity). Among patients with an AFP that was less than 2.50 MOM, the AFP calculation did not include ultrasound measurements in eight of the women.

Additionally, ultrasound was performed during the second or third trimesters in 66 women.

Using ultrasound and AFP screening, they were able to detect 98% of neural tube defects in these patients.

“Other programs may want to reevaluate their experience with the AFP screening test and how well it detects neural tube defects and ventral wall defects. Over time, having an AFP screening test might become an indication for standard ultrasound, both to improve the accuracy of the test and because these anomalies may be detected by the ultrasound,” Dr. Dashe said.

She noted that her study did not (and could not) perform a cost-benefit analysis, which would differ in different populations. She therefore is not recommending routine ultrasound for this indication.

In addition, Dr. Dashe noted a few limitations of this particular study, pointing to its retrospective nature and the fact that these results might not be generalizable in other centers.

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