Diagnostic Yield of Endometrial Sampling by Age in Premenopausal Women with Abnormal Uterine Bleeding: A Retrospective Cross-Sectional Study

Background: An age of 45 years is often used to guide endometrial assessment in abnormal uterine bleeding (AUB), but age is only one component of clinical risk. We described the relationship between age and histopathological yield among premenopausal women who had undergone endometrial sampling. Methods: This single-centre retrospective cross-sectional study analysed the index sampling episodes of 824 women with AUB documented as premenopausal or perimenopausal (January 2022–May 2026). The clinically more consequential endpoint was endometrial intraepithelial neoplasia (EIN)/atypical hyperplasia or carcinoma; the primary statistical outcome was a broader composite that also included hyperplasia without atypia. Modified Poisson regression estimated the adjusted association between age ≥45 years and the primary outcome. Discrimination of age alone and of an exploratory model using variables available before biopsy was compared in 776 complete cases with bootstrap internal validation. Results: EIN/carcinoma occurred in 4/361 (1.1%) women aged <45 years and 25/463 (5.4%) aged ≥45 years (crude RR 4.87, 95% CI 1.71–13.88). The broad outcome occurred in 24/361 (6.6%) and 57/463 (12.3%), respectively (absolute difference 5.7 percentage points, 95% CI 1.6–9.6; adjusted RR 1.62, 95% CI 1.01–2.61; p = 0.047). Results were similar across sensitivity analyses (adjusted RRs 1.52–1.68). With age coded as ≥45 years in both models, the optimism-corrected AUC was 0.686 for the exploratory pre-biopsy model and 0.575 for age alone (difference 0.111, 95% CI 0.060–0.196). Conclusions: Among premenopausal women selected for endometrial sampling, histopathological yield increased with age, and most EIN/carcinoma cases occurred at age ≥45 years, but the adjusted association for the broad outcome was imprecise, and age alone had limited discrimination. Model performance was assessed only internally and only in sampled women; this study cannot establish a biopsy rule for all women with AUB because women not sampled were not observed.