Sensitivities of first trimester PP13 MoMs before and after adjustment to ABO blood groups.

FPR: false positive rate, IUGR: intrauterine growth restriction; LR: likelihood ratio. Sensitivities and specificities were calculated from PP13 multiples of medians (MoMs) using receiver-operating characteristic (ROC) curve analysis. The increased sensitivity further lead to increased positive LR (sensitivity/[1-specificity]) and decreased negative LR ([1-sensitivity]/specificity) and an increase in their ratio (overall LR). Note that overall LRs are more than doubled after adjustment to ABO blood group. Significant increases in the sensitivity of the PP13 test after adjustment to ABO blood groups are shown. *P<0.05, **P<0.005.