Noninvasive Fetal Sex Determination Using Cell-Free Fetal DNA

tive predictive value, 94.8%; area under curve (AUC), 0.993 (95% CI, 0.989-0.995), with significant interstudy heterogeneity. DNA methodology and gestational age had the largest effects on test performance. Methodology test characteristics were AUC, 0.988 (95% CI, 0.979-0.993) for polymerase chain reaction (PCR) and AUC, 0.996 (95% CI, 0.9930.998) for real-time quantitative PCR (RTQ-PCR) (P=.02). Gestational age test characteristicswereAUC,0.989(95%CI,0.965-0.998)(7weeks);AUC,0.994(95%CI,0.9870.997)(7-12weeks);AUC,0.992(95%CI,0.983-0.996)(13-20weeks);andAUC,0.998 (95% CI, 0.990-0.999) (20 weeks) (P=.02 for comparison of diagnostic ORs across age ranges). RTQ-PCR (sensitivity, 96.0%; specificity, 99.0%) outperformed conventional PCR (sensitivity, 94.0%; specificity, 97.3%). Testing after 20 weeks (sensitivity, 99.0%; specificity, 99.6%) outperformed testing prior to 7 weeks (sensitivity, 74.5%; specificity, 99.1%), testing at 7 through 12 weeks (sensitivity, 94.8%; specificity, 98.9%), and 13 through 20 weeks (sensitivity, 95.5%; specificity, 99.1%). Conclusions Despiteinterstudyvariability,performancewashighusingmaternalblood. Sensitivity and specificity for detection of Y chromosome sequences was greatest using RTQ-PCR after 20 weeks’ gestation. Tests using urine and tests performed before 7 weeks’ gestation were unreliable.