Background: The Endometriosis Symptom Diary (ESD) and Endometriosis Impact Scale (EIS) are patient-reported outcome measures developed to evaluate efficacy in clinical trials and clinical practice. The ESD is a daily electronic diary assessing symptom severity; the EIS is a weekly electronic diary assessing symptom impact. This study explored the importance of symptoms (ESD items) and impacts (EIS domains), perspectives on scoring algorithms, and clinically important difference (CID) thresholds to inform clinical trial score interpretation.
Methods: Endometriosis patients in Germany (n = 8) and the US (n = 17), and expert clinicians (n = 4) in Germany, the US, Spain, and Finland participated in semi-structured qualitative interviews comprising structured tasks. Interview transcripts were analyzed using thematic analysis techniques.
Results: Quality and severity of endometriosis-associated pelvic pain varied considerably among patients; some experienced pelvic pain daily, others during menstrual bleeding (dysmenorrhea) only. Patients and clinicians ranked "worst pelvic pain" as the most meaningful pain concept assessed by the ESD, followed by constant and short-term pelvic pain. Preferences for summarizing daily pain scores over the 28-day menstrual cycle depended on individuals' experience of pain: patients experiencing pain daily preferred scores summarizing data for all 28 days; patients primarily experiencing pain during selected days, and their treating clinicians preferred scores based on the most severe pain days. Initial CID exploration for the "worst pelvic pain" 0-10 numerical rating scale (0-10 NRS) revealed that, for most patients, a 2- or 3-point reduction was considered meaningful, depending on baseline severity. Patients and clinicians ranked "emotional well-being" and "limitations in physical activities" as the most important EIS domains.
Conclusions: This study informs the use of the ESD and EIS as clinically relevant measures of endometriosis symptoms and their impact. Findings from the ESD highlight the importance of individual-patient assessment of pain experience and identify "worst pelvic pain" as the most meaningful symptom assessed. Aggregating scores over the 28-day menstrual cycle may inform meaningful endpoints for clinical trials. Diverse EIS concepts (e.g. impact on emotional well-being and physical activities) are meaningful to patients and clinicians, emphasizing the importance of evaluating the impact on both to comprehensively assess treatment efficacy and decisions.
Trial registration: Not applicable. Qualitative, non-interventional study; registration not required.
Keywords: Clinically important difference (CID); Endometriosis; Endometriosis Impact Scale (EIS); Endometriosis Symptom Diary (ESD); Patient preference; Patient-reported outcome measures; Qualitative research; Women’s health.