Factors affecting attrition in a longitudinal study of patients with AIDS

Abstract

Anecdotal data have suggested that retention of HIV-infected patients with immune recovery in longitudinal studies may be difficult as they resume normal activities. This study evaluated risk factors for attrition among patients with AIDS in a cohort study in the era of highly active antiretroviral therapy. Patients with AIDS enrolled in the Longitudinal Study of Ocular Complications of AIDS were evaluated every three months with demographic, clinical and laboratory data collected. Lost to follow-up was defined as any patient who missed all study visits and could not be contacted for 12 consecutive months, who had not died and who did not re-enter the study at a later date. Of the 1,052 patients studied, 77 (7.3%) were lost to follow-up (rate = 0.03/person year). In the multivariate analysis, factors associated with attrition were CD4+ T-cell count category (hazard ratio (HR) = 2.03; 95%CI: 1.01, 4.24; P=0.05 for CD4+ count ≤ 50 cells/µL and HR = 1.96; 95%CI: 1.12, 3.40; P=0.02 for CD4+ count 51–200 cells/µL) and detectable HIV viral load (HR = 1.29; 95%CI: 1.07, 1.53; P<0.001 for HIV viral load >400 copies/mL). These data suggest that patients with compromised immunologic status are at an increased risk for being lost to follow-up.

Acknowledgments

The study was carried out for the Studies of Ocular Complications in AIDS (SOCA) Research Group and was supported by cooperative agreements from the National Eye Institute to the Johns Hopkins University School of Medicine (U10 EY 08052), The Johns Hopkins University Bloomberg School of Public Health (U10 EY 08057) and the University of Wisconsin, Madison School of Medicine (U10 EY 08067). Additional support was provided by the National Center for Research Resources through General Clinical Research Center grants: 5M01 RR 00350 (Baylor College of Medicine); 5M01 RR 00052 (Johns Hopkins University School of Medicine); 5M01 RR 05096 (LSU/Tulane/Charity Hospital); 5M01 RR 00865 (University of California, Los Angeles); 5M01 RR00046 (University of North Carolina); 5M01 RR00043 (University of Southern California); 5M01 RR00047 (Weill Medical College of Cornell University). Support was also provided through cooperative agreements: U01 AI 27674 (Louisiana State University/Tulane); U01 AI 27660 (University of California, Los Angeles); U01 AI 27670 (University of California, San Diego); U01 AI 27663 (University of California, San Francisco); U01 AI25868 (University of North Carolina); U01 AI25903 (Washington University at St. Louis); U01 AI32783 (University of Pennsylvania). For a list of participating clinical centers see appendix.