Self-reported sex partner dates for use in measuring concurrent sexual partnerships: correspondence between two assessment methods.

Although prevalence of concurrent sexual partnerships is increasingly investigated as a driver of HIV epidemics, its measurement varies and its role in transmission dynamics remains contested. Relying on different methods of obtaining self-reported partnership histories may lead to significant differences in prevalence. This study examined the reliability of two methods for assessing dates of sex and the implications for measuring concurrent sexual partnerships. We conducted a cross-sectional reliability study using self-reported survey data from 650 women ages 18-65 years, recruited online nationwide for human papillomavirus natural history studies from 2007 to 2012. Intermethod reliability of first and last sex with the most recent partner was assessed using weighted kappa. Intraclass correlation coefficient was estimated for intramethod reliability across two consecutive questionnaires administered 4 months apart. Point prevalence of concurrent sexual partnerships at 6 months prior to the questionnaire date was similar between the two question formats (10.5 % for categorical and 10.9 % for continuous). The range between the minimum and maximum cumulative prevalence for 12 months was larger when using the categorical questions (17.0-29.6 % compared to 27.6-28.6 % using the continuous questions). Agreement between the two question formats was moderate for the date of first sex with the most recent partner (κ = 0.56, 95 % CI 0.48-0.64) and almost perfect for the date of last sex (κ = 0.93, 95 % CI 0.91-0.94). Longitudinal agreement for date of first sex was high for the continuous date question (ICC = 0.89, 95 % CI 0.86-0.92). Results of this reliability study can be used to inform the design of future studies of concurrent sexual partnerships and their association with HIV.