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Research Letter
August 6, 2008

Sampling-Based Approach to Determining Outcomes of Patients Lost to Follow-Up in Antiretroviral Therapy Scale-Up Programs in Africa

JAMA. 2008;300(5):506-507. doi:10.1001/jama.300.5.506

To the Editor: Evaluating outcomes among the millions of HIV-infected patients starting antiretroviral therapy (ART) in settings with limited resources is key to understanding the effect of current treatment programs and guiding future strategies. Accurately assessing survival outcomes has been precluded by substantial numbers of patients not returning for care. One year after starting ART, 15% to 30% of patients are lost to follow-up.1,2 Only by determining the outcomes of those lost can true survival and program impact be understood. We present a sampling-based strategy to address this.

We evaluated all HIV-infected adults initiating ART in a rural clinic in Mbarara, Uganda, between January 1, 2004, and September 30, 2007. Each month, a tracker sought an unselected and consecutive sample of patients in the community who were lost to follow-up (a 6-month absence from clinic) to obtain their vital status. Naive and corrected estimates of cumulative incidence of mortality were determined with Kaplan-Meier techniques. In the naive estimate, only deaths passively recorded by the clinic through routine processes were included. In the corrected estimate, the updated vital status among the tracked sample of lost patients was used to represent outcomes among all those lost to follow-up by generating a probability weight (the ratio of all patients lost to follow-up to those lost and sampled with subsequent updated vital status) (Figure 1). Lost patients with sampling-updated vital status were assigned this weight, and all other lost patients were dropped from the analysis. This approach is equivalent to previously described methods.3 Comparisons of lost patients with and without vital status ascertainment were tested with χ2 and t tests. Significance was set at P < .05. Analyses were performed using Stata 10 (StataCorp, College Station, Texas). The study was approved by the institutional review boards of the University of California, San Francisco, and the Mbarara University of Science and Technology. Patients gave oral consent.