Carmen J Beamon1, Emily E Hardisty1, Sarah C Harris2, Neeta L Vora1. 1. Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine; University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, USA. 2. University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, USA.
Abstract
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.
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.