Background: Biased enrollment and attrition compromise the power of clinical trials and limit generalizability of findings. We identify predictors of enrollment and retention for HIV-discordant couples enrolled in prospective studies in Zambia.
Principal Findings: A total of 1995 discordant couples were invited to enroll. Predictors of nonenrollment, loss to follow-up, and missed appointments were evaluated using multivariate models. M+F− couples were more likely to be eligible and to enroll and less likely to be lost to follow-up than F+M− couples. Substantial losses to follow-up occurred between testing and enrollment (21.3% of M+F− and 28.1% of F+M−) and between enrollment and the first follow-up visit (24.9% of M+F− and 30.5% of F+M−). Among M+F− and F+M− couples, residence far from the clinic, younger age, and women's age at first intercourse ≤17 years were predictive of attrition. No income, ≤2 lifetime sex partners, no history of sexually transmitted infection in women, and recent extramarital contact in their male partners predicted attrition in F+M− couples.
Conclusions: Discordant couples are critical to observational studies and clinical trials to prevent male-to-female and female-to-male transmission. Retention biases must be taken into account during analysis. Run-in designs that delay randomization may improve retention in clinical trials.
From the *Zambia-Emory HIV Research Project, Lusaka, Zambia; †Department of Epidemiology, Ryals School of Public Health, University of Alabama at Birmingham, Birmingham, AL; ‡Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, GA; §School of Medicine, University of Zambia, Lusaka, Zambia; ∥University Teaching Hospital, Lusaka, Zambia; and ¶Counseling Services Unit, Ministry of Health, Lusaka, Zambia.
Received for publication April 6, 2007; accepted October 4, 2007.
Supported by funding from the Fogarty AIDS International Training and Research Program FIC 2D43 TW001042; the Social and Behavioral Core of the Emory Center for AIDS Research P30 AI050409; National Institutes of Health grants AI23980, AI 40951, HD 40125, MH 66767; and the International AIDS Vaccine Initiative.
This work has previously been presented at the following meetings: Second International AIDS Society Conference on HIV Pathogenesis and Treatment, Paris, France, July 13-17, 2003 (oral presentation and abstract 159), and AIDS Vaccine 2003 Conference, New York, NY, September 18-21, 2003 (oral presentation).
Correspondence to: Susan Allen, MD, MPH, DTM&H, Hubert Department of Global Health, Rollins School of Public Health, Emory University, 1520 Clifton Road NE, Suite 234, Atlanta, GA 30322 (e-mail: firstname.lastname@example.org, www.rzhrg.org).