Managing Pregnancies of Unknown Location With the M4 Prediction Model or the NICE Algorithm: A Randomised Controlled Trial With Cross‐Sectional Diagnostic Accuracy Data

ABSTRACT

Objective

To determine the diagnostic performance and clinical utility of the M4 prediction model and the NICE algorithm managing women with pregnancy of unknown location (PUL).

Design

The study has a superiority design regarding specificity for non-ectopic pregnancy for M4, given that the primary outcome of sensitivity for ectopic pregnancy (EP) is non-inferior in comparison with the NICE algorithm.

Setting

Emergency gynaecology units in Sweden.

Population

595 women with PUL.

Methods

Participants were randomised (1:1) to M4 or the NICE algorithm after two serum human chorionic (hCG) levels and were categorised as high or low risk of having an EP. The diagnostic performance was evaluated on cross-sectional data and utility by parallel groups.

Main Outcome Measures

The proportion of EP categorised as high risk (sensitivity) and non-ectopic pregnancies categorised as low risk (specificity). Clinical outcomes were assessed.

Results

The sensitivity for EP was 79% (115 of 146) for M4 versus 85% (124 of 146) for the NICE algorithm, p = 0.1496 and the specificity for non-ectopic pregnancies was 67% (300 of 449) for M4 and 74% (334 of 449) for the NICE algorithm, p = 0.0003. Clinical outcomes were similar between groups.

Conclusions

The sensitivity for EP by M4 was non-inferior to NICE, but specificity was better for the NICE algorithm. No between group differences were observed for clinical outcomes.

Trial Registration

NCT 03461835, https://www.clinicaltrials.gov