Concordance of Risk Behavior Reporting in Injecting Partnerships Between Young Injection Drug Users in San Francisco

Purpose: Young injection drug users (IDU, under age 30) usually inject with other IDU, and risk behaviors that increase the likelihood of blood-borne disease transmission commonly occur within injecting partnerships. However, self-reported injecting behavior may be subject to reporting bias, therefore we sought to estimate the degree of concordance of reporting injecting risk behaviors between injecting dyads Methods: From May 2006 to October 2011 we enrolled 53 injecting partnerships that were hepatitis C virus (HCV) discordant on RNA testing in San Francisco, California. Each partnership was followed prospectively for up to one year. Monthly interviews from each partner were date-matched and responses to risk behavior questions were compared. Concordance of reporting of injecting risk behaviors was estimated with the Kappa statistic. Results: Participants had a median age of 26, IQR:23-28 and median years injecting of 8.1, IQR:3.1 – 10.8. Forty percent of the injecting partnerships were also sexual partnerships while 60% were solely injecting partnerships. Sixty percent were female-male and 38% were male-male partnerships. At enrollment, 27%, 24%, 34% and 33 % of the participants reported engaging in receptive syringe sharing, distributive syringe sharing, receptive cooker sharing , and distributive cooker sharing with their partners in the prior month. Dyad concordance for these behaviors was 79%, 86%, 81% and 74% respectively. Conclusions: Injecting partners reported frequent cooker sharing and less frequent syringe sharing. We observed moderately high agreement in reporting of injection risk behavior in partnership dyads. This suggests that self-reported risk behavior within partnerships may be a valid way to measure partner-specific injecting risk.