Diagnostic accuracy of fetal rhesus D genotyping using cell-free fetal DNA during the first trimester of pregnancy.

BACKGROUND: Rhesus D genotyping with cell-free fetal DNA currently is used throughout the world. Although this technique has spread rapidly, its optimal use is still a matter of debate. This screening test has been introduced mainly for the treatment of RhD-negative pregnant women during the third trimester of pregnancy, thereby avoiding systematic anti-D prophylaxis, yet such a strategy has proved cost-ineffective. Publications reporting on fetal RHD genotyping with cell-free DNA in maternal plasma, specifically during the first trimester of pregnancy, are scarce in the scientific literature. OBJECTIVE: This study sought to assess the performance of noninvasive fetal Rhesus D genotyping in the first trimester of pregnancy with a single-exon real-time polymerase chain reaction assay. STUDY DESIGN: This was a retrospective observational multicenter study. Cell-free fetal DNA was extracted from maternal blood of both nonimmunized and immunized women at 10-14 weeks of gestation. RHD sequence was determined by quantitative polymerase chain reaction, with amplification of exon 10. Results were compared with RhD phenotype data that were obtained by cord blood sampling of neonates. RESULTS: In total, 416 serum samples from RhD-negative pregnant women were collected during the first trimester of pregnancy. The test's overall sensitivity and specificity were 100% (95% confidence interval, 96.9-100.0) and 95.2% (95% confidence interval, 90.5-97.6), respectively. The negative and positive predictive values were 99.8% (95% confidence interval, 94.9-100.0) and 97.1% (95% confidence interval, 94.2-98.6), respectively. Fetal RHD status was inconclusive in 9 cases (2.2%). CONCLUSION: Noninvasive fetal RHD determination by single-exon quantitative polymerase chain reaction during the first trimester of pregnancy exhibits high accuracy.

Diagnostic Performance of a New Rapid Lateral Flow Immunoassay in Patients Suspected of Heparin-Induced Thrombocytopenia and Its Clinical Consequences.

We prospectively evaluated the diagnostic accuracy of a new rapid assay (STic Expert HIT) alone or in combination with a clinical score in 90 HIT-suspected patients. The 4Ts score was calculated, and ELISA and serotonin-release assay (SRA) were performed; the average time taken for test results were 2 and 5 days for ELISA and SRA, respectively. The STic test was performed in our laboratory as an evaluation exercise and the result was available in 1 hour, but results were not communicated to the clinicians so as to not influence management. Diagnostic performance of STic test was assessed, alone and in combination with 4Ts score. HIT was diagnosed in 19 patients. The sensitivity, specificity, and positive and negative predictive values for the STic test alone were 95%, 92%, 75%, and 98%, respectively, with an accuracy of 92%. The likelihood ratio for positive and negative results with the STic test was 11.2 and 0.06. The combination of the 4Ts score and the STic test results had a negative predictive value of 100% and a negative likelihood ratio of 0. The favorable performance of the STic test may allow for the rapid exclusion of HIT in combination with a low to intermediate pretest clinical probability. During the subsequent year, using the STic test in real time to rapidly exclude the diagnosis, we observed a 50% reduction in danaparoid administration in HIT-suspected patients.