Prediction of fetal anemia in pregnancies with red‐cell alloimmunization: comparison of middle cerebral artery peak systolic velocity and amniotic fluid OD450

Abstract

To compare the accuracy of Doppler velocimetry (middle cerebral artery peak systolic velocity, MCA-PSV) and amniocentesis (amniotic fluid delta optical density 450 (OD450)) for the detection of fetal anemia against the gold standard of fetal blood sampling (FBS). Thirty-eight pregnancies were identified to be at risk of fetal anemia from immune causes between January 2000 and May 2002. In a cross-sectional diagnostic accuracy study, MCA-PSV and amniotic fluid delta OD450 values were plotted on reference charts and compared to an FBS obtained within the subsequent 7 days. Receiver-operating characteristics (ROC) curves were used and the area under the curve (AUC) calculated to compare the overall accuracy of the two tests. Sensitivity, specificity and likelihood ratios for positive (LR+) and negative (LR-) test results were generated for specific thresholds of MCA-PSV and delta OD450. For MCA-PSV (n = 38), the AUC was 0.71 (95% CI 0.57-0.85) and for amniotic fluid delta OD450 (n = 22) it was 0.68 (95% CI 0.49-0.87) compared with FBS within 7 days. Sensitivity, specificity and LR+, LR- for MCA-PSV were 64%, 81%, 3.4 and 0.5, respectively, and 53%, 71%, 1.9 and 0.7 for amniotic fluid OD450, respectively. MCA-PSV and OD450 have similar test accuracy in detecting fetal anemia. MCA-PSV is non-invasive and therefore presents no risk of miscarriage or preterm labor and thus is a preferable method of screening for fetal anemia.