The ENDOPAIN 4D Questionnaire: A New Validated Tool for Assessing Pain in Endometriosis

Objectives: To study the measurement properties, the responsiveness and the minimal clinically important difference of the ENDOPAIN-4D: a new questionnaire for assessing pain in endometriosis. Methods: A prospective, observational, multicentre study was conducted including all women ≥18 years consulting for symptomatic proven endometriosis between 1 January 2017 and 30 June 2018 and volunteering to participate. Each patient had to answer a new self-administered patient-reported outcome (PRO) questionnaires (the ENDOPAIN-4D) at inclusion (T0) and 12 months after medical or surgical treatment (T1). Criteria defined by COSMIN were used to validate the questionnaire’s measurement properties. The minimal clinically important difference was estimated by the anchor-based method. Results: The study included 199 women. The ENDOPAIN-4D score had a four dimensional structure with good internal consistency (measured by Cronbach α): (I) pain-related disability (α = 0.79), (II) painful bowel symptoms (α = 0.80), (III) dyspareunia (α = 0.83), and (IV) painful urinary tract symptoms (α = 0.77). They produced four subscores that can be summed to obtain a single score (α = 0.61). The ENDOPAIN-4D total score ranged from 0 to 94.00 (mean ± SD: 46.7 ± 22). The total score was significantly correlated with the PROs used in endometriosis. Sensitivity to change was good with large effect sizes (ES) (mean of the differences: 36.3 p = 1.8 10(−7), ES 0.76). The minimal clinically important difference of the global score was determined to be 10.9. Conclusions: The ENDOPAIN-4D questionnaire is easy to use, valid, and effective in assessing patient reported pain symptoms in women treated for endometriosis. This new instrument can be used as the primary outcome for future clinical trials and as a tool for routine patient follow-up.