Purpose: Massively parallel sequencing to detect fetal aneuploidy has high sensitivity and specificity for the detection of trisomies 21, 18, and 13 in high-risk populations. The purpose of our study was to review our institution's experience with the use of noninvasive prenatal testing for aneuploidy screening.
Methods: This was a descriptive study of patients who had undergone noninvasive prenatal testing between January and September 2012 at the UNC Prenatal Diagnosis unit.
Results: Two hundred and eight women had undergone noninvasive prenatal testing during the study period. The majority of patients were white (62.9%) and of advanced maternal age (71.2%). The fetal fraction was below the threshold in three obese patients (1.4%). An abnormal noninvasive prenatal test (aneuploidy detected or "unclassified" result) was reported in 6.3% (13/208) of the patients. Noninvasive prenatal testing had a combined sensitivity of 87.5% and specificity of 99.5% for detection of trisomies 21, 18, and 13. There were "unclassified" results in 11.1% (5/45) of the patients. Over the study period, the number of patients requesting noninvasive prenatal testing increased monthly. The rate of amniocenteses significantly declined (8.1% before vs. 5.3% after noninvasive prenatal testing, P < 0.01).
Conclusion: An increase in uptake of noninvasive prenatal testing and a significant decline in amniocentesis procedures were observed. The rates of "unclassified," false-positive, and false-negative results were higher than anticipated based on published preclinical trials.