Placental protein 13 as an early marker for pre-eclampsia: a prospective longitudinal study

Objective To assess the value of placental protein 13 (PP13) as an early marker of pre-eclampsia. Design Sequential blood samples were obtained from women with singleton viable pregnancies at 6-10, 16-20 and 24-28 weeks of gestation. Samples were tested for PP13 using a solid-phase sandwich enzyme-linked immunosorbent assay. Levels were expressed as multiples of the medians (MoM) of the unaffected population. The slope or rate of change in PP13 concentration per week of gestation was also calculated. Setting Thirty-five prenatal care community clinics. Sample In total, 1366 women were recruited, and subsequently, 20 were diagnosed with pre-eclampsia, 41 with gestational hypertension and 1178 were unaffected. Main outcome measures Sensitivity and specificity of screening with PP13 at each gestational period and of PP13 level combined with the slope of PP13 between two testing periods. Results At 6-10 gestational weeks, PP13 levels were significantly lower among the pre-eclampsia group with a median 0.28 MoM (95% CI 0.15-0.39, P < 0.004). Using a cutoff of 0.40 MoM, the sensitivity was 80%, false-positive rate (FPR) was 20% and odds ratio was 16.0 (95% CI 5.3-48.4). Combining MoM of 6-10 weeks and slope between 6-10 and 16-20 weeks, the sensitivity was 78%, the FPR was 6% and odds ratio was 55.5 (95% CI 18.2-169.2). The gestational hypertension group was not different from the normal group. Conclusions PP13 in the first trimester alone or in combination with the slope between the first and the second trimesters may be a promising marker for assessing the risk of pre-eclampsia.