Retrospective validation study of miniPIERS prediction model in Zanzibar

Objective: To perform a retrospective external validation of miniPIERS in Zanzibar's referral hospital. Methods: From February to December 2017, data were collected retrospectively on all cases of hypertensive disorders of pregnancy (HDP) admitted to Mnazi Mmoja Hospital, Zanzibar, Tanzania. The primary outcome was the predictive performance of miniPIERS by examining measures of discrimination, calibration, and stratification accuracy. The secondary outcome was the applicability of miniPIERS within the referral hospital setting. Results: During this period, 2218 of 13 395 (21%) patients were identified with HDP, of whom 594 met the inclusion criteria. Sixty per cent of patients with adverse outcomes were excluded because they had experienced one of the adverse outcomes before admission. The discriminative ability of miniPIERS was inaccurate. It was not likely to aid risk stratification because of low sensitivity and low positive predictive value. The model showed fair discrimination in HDP before 34 weeks of gestation (area under the receiver operating characteristics curve 0.72, 95% confidence interval 0.63–0.82). Conclusions: The benefit of miniPIERS appeared to be limited, although clinical conditions make any validation challenging. Its application for risk stratification in preterm pregnancies should be further investigated.