Objective: To evaluate the screening efficacy of second-trimester maternal serum inhibin-A combined with uterine artery Doppler studies performed at 20 weeks' gestation for the prediction of pre-eclampsia.
Methods: Six hundred and eighty-nine consecutive unselected women who had inhibin-A levels measured between 15 and 19 weeks' gestation subsequently had color flow pulsed Doppler of both uterine arteries at the time of the anomaly scan (mean 20.5, range 18-22 weeks' gestation). The main outcome measures were pre-eclampsia and pre-eclampsia requiring delivery before 37 weeks' gestation. The presence or absence of notches in the flow velocity waveform was noted, and the resistance index measured. Receiver operator curves were created for inhibin-A and uterine artery Dopplers alone and in combination. Sensitivities for each method were compared at false-positive rates of 3% and 7%.
Results: Thirty-five women developed pre-eclampsia, of whom 15 required delivery before 37 weeks' gestation. For a false-positive rate of 7%, the sensitivity using bilateral notches/mean resistance index > or = 0.65 was 60% with a positive likelihood ratio of 8.6 (confidence interval 5.7-12.6). For the same false-positive rate, when bilateral notches/mean resistance index > or = 0.55 and unilateral notches/mean resistance index > or = 0.65 were combined with inhibin-A > or = 1.0 multiples of the median, the sensitivity improved to 71% and the positive likelihood ratio to 10.8 (confidence interval 7.4-15.4). For pre-eclampsia requiring delivery before 37 weeks for a false-positive rate of 3%, the sensitivity for bilateral notches improved from 27% to 60% and the positive likelihood ratio improved from 9.2 to 20.8 when uterine artery notch data was combined with inhibin-A. The improvement in sensitivity for the combined method, compared to either inhibin-A or uterine artery Dopplers alone, was statistically significant for both pre-eclampsia ( P < 0.05) and preterm pre-eclampsia ( P < 0.02).
Conclusion: Combination of second-trimester serum inhibin-A and uterine artery Doppler at 20 weeks improves the screening efficacy for the prediction of pre-eclampsia especially when this necessitates early delivery. This combination might form the basis of an effective and practical early screening test for the condition.