The Most Impactful Symptom of Endometriosis Questionnaire (MISE-Q): a cognitive interview study

Endometriosis is a condition with symptoms that vary widely, often affecting daily activities and quality of life. A patient-centered approach to identifying and measuring the most important symptoms has been recommended in the core outcome set for endometriosis clinical trials, yet no such instrument currently exists. This study aimed to pilot-test a new patient-reported outcome measure, the "Most Impactful Symptom of Endometriosis Questionnaire" (MISE-Q), designed to address this gap.

The MISE-Q's content validity was evaluated through cognitive interviews using the Three-Step Test-Interview method. Participants with a surgical diagnosis of endometriosis were recruited and interviewed across five iterative rounds.

Thirty-four interviews were conducted, revealing diverse symptom experiences. Most participants appreciated the person-centered nature of the instrument, though some found it difficult to choose a single "most impactful symptom" due to overlapping symptoms. A three-month recall period was supported to capture symptom fluctuation over time. Clinician and researcher feedback was incorporated to improve clarity, usability, and feasibility. The MISE-Q was revised, including changes to symptom wording, and the removal of two symptoms and the addition of one. A free-text option was included to capture additional symptoms due to the condition's heterogeneity. Participants praised the MISE-Q's brevity and clear language.

The final instrument offers a comprehensive tool to measure the "most impactful symptom" of endometriosis. While it represents the most rigorously developed option available for this purpose, its use in clinical trials should be preceded by field testing to establish additional measurement properties and assess cultural relevance across populations.