701: Serum Concentration of Placental Protein 13 (PP13) in Pregnant Women is Influenced by Maternal Blood Group

Placental Protein 13 (PP13) is a galectin, which binds beta-galactosides. In previous studies, maternal serum PP13 multiple of the medians (MoM) adjusted to gestational age (GA), body mass index, maternal age, ethnicity, and parity was found to predict preeclampsia with sensitivity of 85% at 20% false positive rate (FPR) based on first trimester MoM. For the same sensitivity, FPR reduced to 6% when the slope between PP13 concentrations during the first and second trimesters were sequentially evaluated with first trimester PP13 MoM. The objective of this study was to examine maternal serum PP13 MoMs in the first and second trimesters of pregnancy in relation to maternal ABO and Rhesus (Rh) blood groups. Sequential blood samples were obtained from 1366 women with singelton viable pregnancies at 6-10, 16-20 and 24-28 weeks. PP13 concentrations were measured by ELISA. ABO and Rh blood groups were determined by a standard tile technique. ABO and Rh blood groups were added as additional confounders to the PP13 MoM algorithm. P<0.05 was considered significant. The prevalence of blood groups in the cohort was 46% O, 43% A, 8% B and 3% AB. Rh negative women were 6%. Median PP13 MoMs were higher in women with blood group B than in women with other blood groups in all three comparisons [at GA 6-10: B=1.26, AB=0.93(P<0.01), O=1.07, A=0.78; at GA 16-20: B=1.84, AB=0.94(P<0.01), O=1.05, A=0.88; and at GA 24-28: B=1.32, AB=0.72(P<0.01), O=1.12(P<0.05), A=0.87]. The Rh factor had no effect on PP13 MoMs at any of the time periods examined. The results are consistent with the high-affinity of PP13 to N-acetyl-galactosamine present on group A antigen and its lower affinity to galactose present on group B antigen. Our results suggest that maternal blood group should be considered as another important confounder in adjustment of PP13 MoMs that may improve preeclampsia prediction.