Responsiveness and thresholds for clinically meaningful changes in worst pain numerical rating scale for dysmenorrhea and nonmenstrual pelvic pain in women with moderate to severe endometriosis.

Objective To evaluate the utility, responsiveness, and thresholds for clinically meaningful change of a numerical rating scale for worst pain associated with dysmenorrhea (NRS-DYS) and nonmenstrual pelvic pain (NRS-NMPP) in women with moderate to severe endometriosis-associated pain. Design Analysis of data from two phase III randomized clinical trials (EM-I [NCT01620528] and EM-II [NCT01931670]). Setting Not applicable. Patient(s) Premenopausal women ages 18–49 years with moderate to severe endometriosis-associated pain. Intervention(s) Participants in both trials were randomized 3:2:2 to receive placebo, elagolix 150 mg once daily, or elagolix 200 mg twice daily for 6 months. Main Outcome Measure(s) NRS-DYS and NRS-NMPP. Result(s) EM-I enrolled 871 women and EM-II enrolled 815 women. For patients with a global impression of improvement at month 3, the least-squares mean change between baseline and month 3 was −3.6 (EM-I and EM-II) for NRS-DYS and −1.9 (EM-I) and −2.0 (EM-II) for NRS-NMPP. Standard errors of measurement were 2.99 (EM-I) and 2.86 (EM-II) for NRS-DYS and 1.74 (EM-I) and 1.71 (EM-II) for NRS-NMPP. Baseline half standard deviations were 0.78 (EM-I) and 0.85 (EM-II) for NRS-DYS and 0.92 (EM-I) and 0.96 (EM-II) for NRS-NMPP. Based on these results, clinically meaningful changes were defined as a reduction of 4 points for NRS-DYS and 2 points for NRS-NMPP. Conclusion(s) This study demonstrated the utility and responsiveness of separate numerical rating scales to assess worst pain for dysmenorrhea and NMPP in women with moderate to severe endometriosis-associated pain and identified initial thresholds for clinically meaningful change.