THE PREDICTIVE VALUE OF MATERNAL SERUM TESTING FOR DETECTION OF FETALANEMIA IN RED-BLOOD-CELL ALLOIMMUNIZATION

OBJECTIVE: Current management protocols for pregnancies complicated by red blood cell alloimmunization use the maternal antibody titer to pr edict the need for invasive testing for detection of fetal anemia. We investigated the use of three maternal serum tests to assess their use fulness in predicting fetal disease: indirect Coombs' titer, Marsh sco re, and monocyte monolayer assay. STUDY DESIGN: Forty-seven serum samp les from pregnant women with red blood cell antibodies associated with fetal anemia were analyzed at cordocentesis. Fetal blood was analyzed for hematocrit (corrected for gestational age) and antigen status. Fe tal anemia was defined as a hematocrit value of <2 SD from the mean va lue for gestational age. Fetuses were classified into three groups: An tigen positive with anemia (n = 19), antigen positive without anemia ( n = 17), antigen negative (n = 11). Statistical methods included Krusk al-Wallis test, Newman-Keuls test, Spearman's rank correlation, and re ceiver-operator characteristic curves; p < 0.05 was considered signifi cant. RESULTS: The median monocyte monolayer assay (phagocytosis, adhe rence, and association) did not differ among the three groups. Both ma ternal titers and Marsh scores were significantly higher in fetuses wi th anemia compared with the other two groups of fetuses (256 vs 64 vs 64, p < 0.001, and 86 vs 69 vs 64, p = 0.02, respectively). Both titer and Marsh score exhibited significant correlations with corrected fet al hematocrit (r = -0.70, p < 0.001; r = -0.63, p < 0.001, respectivel y). Comparison of the overall receiver-operator characteristic curves for titer and Marsh score revealed no statistical difference; however, a Marsh score of 57 was noted to have a superior specificity than a t iter of 16 (p = 0.02). CONCLUSION: The maternal Marsh score can be per formed in conjunction with standard indirect Coombs' titers to enhance the predictability of fetal anemia.