Right Censoring and Mortality in the Multicenter AIDS Cohort Study and Women's Interagency HIV Study

Epidemiologists frequently employ right censoring to handle missing outcome, covariate, or exposure data incurred when participants have large gaps between study visits or stop attending study visits entirely. But, if participants who are censored are more or less likely to experience outcomes of interest than those not censored, such censoring could introduce bias in estimated measures.

We examined how censoring after two consecutive missed visits may affect mortality results from the Multicenter AIDS Cohort Study (MACS) and Women's Interagency HIV Study (WIHS). MACS and WIHS provide linkages to vital statistics registries, such that mortality data were available for all participants, regardless of whether they attended study visits.

In a gold standard analysis that did not censor after two consecutive missed visits, 10-year mortality was 23% (95% CI: 22, 24) in MACS and 21% (95% CI: 20, 23) in WIHS. Estimated mortality was modestly reduced by 0%-5% across subgroups when censoring at missed visits. Applying inverse probability of censoring weights partially removed this attenuation.

While mortality was slightly elevated after two consecutive missed visits in MACS and WIHS, censoring at two consecutive missed visits did not substantially alter estimated mortality, particularly after applying inverse probability of censoring weights.