OBJECTIVES: To generate evidence on patient preferences concerning medication attributes among UK patients with endometriosis-related pain.

METHODS: An online discrete choice experiment among endometriosis patients diagnosed 0.5-10 years ago and without confounding pain conditions. Attributes and levels were defined from literature search, expert and patient interviews. The design included 12 choice sets, each consisting of two alternative fictitious treatments and a No treatment option. A pilot study was conducted and a subset did a cognitive-debriefing interview. A D-efficient design was used for the full study. Analyses included a conditional logit model with interactions.

RESULTS: The attributes following qualitative research were: mode of administration, ability to conceive, worst level of (i) pelvic pain, (ii) period pain, (iii) pain during intercourse, need for pain medication (days/month), fracture risk and out-of-pocket costs. Following pilot analysis (n=30) and patient interviews (n=10), minor wording and format changes were made. The full study included 200 participants. Participants’ average age was 32.5 (19-42), 58.5% used hormonal contraceptives, 71% wanted (more) children, and 45% were dissatisfied with current pain treatment; 78% of patients always took pain treatment during their periods, 79% reported a period pain-level of 7-10. Of pain types, period pain had the most influence; patients’ WTP was £36.39 for a period pain-level of 4-6. “Ability to conceive” was valued at £20.51/month and participants preferred options without fracture risk (£13.51/month). Both of these are limitations with current treatments. Treatment at a lower cost was preferred, as were oral tablets over vaginal rings and weekly injections.

CONCLUSIONS: The most important pain type was period pain, perhaps influenced by the fact that 75% of participants experienced severe period pain. Overall lack of preference for vaginal rings should be interpreted with caution as interviews highlighted patients’ lack of awareness of this device. A treatment allowing patients to conceive was appreciated.