Reliability and validity of the 30-second chair-stand test for assessing functional capacity in women with endometriosis: a cross-sectional and longitudinal study

Abstract

INTRODUCTION: and Hypothesis: Endometriosis often causes pelvic pain, limiting movement and physical function. Performance-based tests are fundamental to measure functional status among these women. This study aimed to evaluate the reliability and validity (cross-sectional and longitudinal) of the 30-Second Chair-Stand Test (30CST) in women with endometriosis. METHOD: Observational longitudinal study from a specialized unit of a hospital. Participants completed a sociodemographic and clinical questionnaire. Functional performance was assessed using the 30CST at three time points: T1: In-clinic, baseline; T2: At home, pre-menstruation; T3: At home, during menstruation. Reliability was assessed via intraclass correlation coefficients (ICC) using a 2-way mixed-effects model. Minimal Detectable Change (MDC) was also calculated. Longitudinal validity was tested via two hypotheses supported by the fact that functional performance in women is significantly worse on menstrual phase, when compared to the premenstrual phase, through paired t-tests and standardized response means (SRM). Cross-sectional validity was assessed by comparing 30CST performance between pain groups (cut-off: 7). RESULTS: 54 women participated with mean baseline pain 3.52 ± 3.21, and average 30CST performance ?15 repetitions. Reliability was high across all contexts (ICC: 0.985, 0.975, and 0.981 at T1, T2, and T3, respectively). Performance during menstruation (T3) was significantly lower than pre-menstruation (T2) (mean difference=-1.22 repetitions, p < 0.001; SRM=-0.436). Cross-sectional validity showed that women with high baseline pain (?7) performed significantly fewer repetitions than those with lower pain scores (p < 0.001), with a large effect size (Cohen's d = 1.59). CONCLUSION: The 30CST is a simple and reliable test with strong validity for women with endometriosis.