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

Abstract

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.

Keywords: Endometriosis; dysmenorrhea; nonmenstrual pelvic pain; numerical rating scale; pain.