Performance of QUiPP App v.2 tool for prediction of preterm birth in asymptomatic high-risk women attending preterm specialist clinic: external validation study.

Objective: To validate externally the QUiPP App v.2 algorithms in an independent cohort of high-risk asymptomatic women attending a preterm birth (PTB) surveillance clinic in Ireland.

Methods: This was a retrospective, single-center, observational study assessing discrimination and calibration of the QUiPP App v.2 at six predetermined clinical timepoints (PTB at < 30, < 34 and < 37 weeks of pregnancy and PTB within 1, 2 and 4 weeks of testing). Discrimination was assessed by estimating the area under the receiver-operating-characteristics curve (AUC) and sensitivity at fixed false-positive rates of 5%, 10% and 20%. Model calibration was assessed to evaluate the concordance between expected and observed outcomes. P-values < 0.05 were considered statistically significant. No adjustments for treatment effects were made.

Results: Overall, 762 women with 1660 PTB surveillance clinic visits using the QUiPP App v.2 between 2019 and 2022 were analyzed. The study population included 142 (18.6%) patients who later experienced PTB. The QuiPP App's performance in the prediction of short-term outcomes, such as birth within 1 week (AUC, 0.866 (95% CI, 0.755-0.955)), 2 weeks (AUC, 0.721 (95% CI, 0.569-0.854)) and 4 weeks (AUC, 0.775 (95% CI, 0.699-0.842)), and delivery at < 30 weeks (AUC, 0.747 (95% CI, 0.613-0.865)), was superior to its ability to predict longer-term outcomes (PTB at < 37 weeks: AUC, 0.631 (95% CI, 0.596-0.668)). Calibration was generally good for low-risk results, as the predicted risk in these patients tended to match the observed incidence. However, in women deemed to be at greater risk of PTB, the predicted probability superseded the observed incidence of PTB.

Conclusions: The QUiPP App v.2 accurately discriminates women who are at short-term risk of PTB. A 'treatment paradox' may influence calibration in high-risk women. Further research is needed to ascertain if QuiPP treatment thresholds can be safely adjusted in women receiving prophylactic treatment to prevent PTB, and whether this improves the outcome. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.