Association of site-specific and participant-specific factors with retention of children in a long-term pediatric HIV cohort study

Abstract

Minimizing loss to follow-up (LTFU) in long-term cohort studies is essential for reducing bias and maintaining statistical stability. However, factors associated with attrition of children in observational studies have received little attention. The authors used survival analysis methods to evaluate the association of participant and site characteristics with time to LTFU in a multicenter cohort study conducted in the United States of 2,693 human immunodeficiency virus (HIV)-infected and 1,370 HIV-exposed-but-uninfected children enrolled in 2000-2004. As of 2004, 91% of HIV-infected and 86% of uninfected children had been retained in the study. Among the HIV infected, factors associated with higher risk of LTFU included site prohibition of participant compensation, low caregiver educational level, age >15 years, and higher viral load, whereas death of a family member was associated with better retention. Among uninfected children, sites accruing low numbers of subjects, social worker responsible for retention, young age (1-2 years), and birth abnormalities were associated with higher risk of LTFU. Occurrences of certain stressful life events, such as a death in the family or financial instability, were associated with higher retention, but risk of LTFU increased when children started school or mothers began employment. Although participant characteristics are difficult to modify, the authors identified several potentially modifiable site practices that could be targeted to improve retention.

FIGURE 1

Kaplan-Meier estimates of probability of loss to follow-up over time by human immunodeficiency virus (HIV) infection status, for 2,693 HIV-infected and 1,370 HIV-exposed uninfected children and adolescents enrolled between 2000 and 2004 in a US-based multisite cohort study, Pediatric AIDS Clinical Trials Group (PACTG) 219C. Participants who died, completed the study, or were lost to follow-up because of site closure were censored as of their last study visit, along with those who remained in the study as of July 2004.