Circulating mRNA for the PLAC1 Gene as a Second Trimester Marker (14-18 Weeks' Gestation) in the Screening for Late Preeclampsia

OBJECTIVE: To develop a model for prediction of late preeclampsia (PE; which develops at or after 34 weeks' gestation) based on maternal history and characteristics, mean arterial pressure (MAP), and circulating levels of mRNA for the placenta-specific 1 (PLAC1) gene in maternal plasma at 14-18 weeks' gestation. METHOD: This was a screening study of singleton pregnancies at 14-18 weeks' gestation including 43 women that subsequently developed PE and 200 that were unaffected by PE. A Gaussian model was fitted to the log distribution of the multiple of the median (log MoM) PLAC1 mRNA in the PE group and in the unaffected group. Likelihood ratios for log MoM of circulating levels of mRNA for the PLAC1 gene were used to combine the a priori risk from maternal characteristics with MAP to produce patient-specific risks for each case. RESULTS: Screening by maternal characteristics (including BMI, woman's mother's history of PE, previous PE, and parity) (a priori risk) and MAP detected 46.8% of all cases of late PE at a fixed false-positive rate (FPR) of 10%. The addition of PLAC1 yielded a detection rate (DR) of 62.8% at the same level of FPR. PLAC1 alone yielded a DR of 30.2%. CONCLUSION: In late PE, molecular markers can be used to improve the DR of screening and can be a valid option for the biochemical approach.