SSEs are a measure of sexual activity rather than desire. Sexual event frequency and satisfaction are not parts of the diagnosis or definition of HSDD largely because the frequency of sexual experiences is affected by confounding factors such as pressure from a partner or nonsexual needs for physical comfort or intimacy. In light of these considerations, FDA’s 28 October 2014 expert panel on development of drugs for FSD recommended repositioning SSEs from a primary to a secondary endpoint in future studies of HSDD drugs.
Desire was measured by two different instruments: FSFI-Desire (the sexual desire domain of the Female Sexual Function Index) and eDiary Desire. Sexual desire was measured as mean change from baseline to Week 24 in FSFI-Desire score which is a single domain of the larger FSFI PRO. The two items in the FSFI-Desire are:
1. Over the past 4 weeks, how often did you feel sexual desire or interest? – answers range from “almost never or never” to “almost always or always”
2. Over the past 4 weeks, how would you rate your level (degree) of sexual desire or interest? – answers range from “very low or none at all” to “very high”
The weighted score of FSFI-Desire ranges from 1.2 to 6.0 with lower scores indicating less desire. Consistent with the time period embedded in the FSFI questions, FSFI-Desire was collected using a 28-day recall period. FSFI is the most frequently used tool for measuring FSD, has been extensively validated and was endorsed by FDA’s 28 October 2014 expert panel on development of drugs for FSD. Specific studies have been conducted to validate FSFI-Desire in the premenopausal HSDD population. A comprehensive review of FSFI-Desire validation is provided in the Appendix H.
In the two early studies sexual desire was also measured as mean change from baseline to Week 24 in monthly sum of responses to an eDiary daily desire question (eDiary Desire), standardized to a 28-day period.
The eDiary Desire asks a patient to “Indicate your most intense level of sexual desire in the last 24 hours [or] since your last visit”. Possible responses were “strong”, “moderate”, “low” or “none.” A measure of sexual desire was recorded by eDiary on a daily basis. Reporting of sexual desire information was limited to a 24-hour retrospective period.