Responsiveness and minimal clinically important difference of the EQ-5D-5L in cervical intraepithelial neoplasia: a longitudinal study.

BACKGROUND With the widespread clinical application of the five-level version of the EuroQol five-dimensional questionnaire (EQ-5D-5L), whether the questionnaire scores are responsive to changes in patients' health and how much changes in questionnaire scores represent patients' real health changes require consideration. Consequently, we assessed responsiveness and estimated the minimal clinically important difference (MCID) of the EQ-5D-5L in surgically treated patients with cervical intraepithelial neoplasia (CIN) to determine the relationship between MCID and minimal detectable change (MDC). METHODS We conducted a longitudinal, observational study. Participants were patients with CIN from the gynecology inpatient department of a grade-A tertiary hospital in Shihezi, Xinjiang, China. Participants completed the EQ-5D-5L and the Global Rating of Change Questionnaire (GRCQ) at baseline and one month post-surgery. The Wilcoxon signed-rank test was used to compare EQ-5D-5L scores pre- and post-treatment. We calculated the effect size (ES) and the standardized response mean (SRM) to quantitatively assess responsiveness. Distribution-based, anchor-based, and instrument-defined methods were used to estimate MCID. MCID to MDC ratios at individual- and group-levels were also calculated. RESULTS Fifty patients with CIN completed the follow-up investigation (mean age 44.76 ± 8.72 years; mean follow-up time 32.28 ± 1.43 days). The index value and EQ visual analogue scale (EQ VAS) of the EQ-5D-5L improved by 0.025 and 6.92 (all p < 0.05) at follow-up as compared to baseline respectively. The ES and the SRM of the index value were 0.47 and 0.42 respectively, indicating small responsiveness; while the ES and the SRM of EQ VAS were 0.50 and 0.49 respectively, indicating small to moderate responsiveness. The average (range) of MCIDs for index value and EQ VAS were 0.039 (0.023-0.064) and 5.35 (3.12-6.99) respectively. These values can only be used to determine whether patients have experienced clinically meaningful health improvements at the group level. CONCLUSIONS The EQ-5D-5L has only small to moderate responsiveness in post-surgical patients with CIN, and the MCIDs developed in this study can be used for group-level health assessment. However, further study is needed concerning health changes at the individual level.