title: Comparison of methods for correction of mortality estimates for loss to follow-up after ART initiation: a case of the Infectious Diseases Institute, Uganda.
abstract: BACKGROUND
  In sub-Saharan Africa, a large proportion of HIV positive patients on antiretroviral therapy (ART) are lost to follow-up, some of whom are dead. The objective of this study was to validate methods used to correct mortality estimates for loss-to-follow-up using a cohort with complete death ascertainment.
  
  
  METHODS
  Routinely collected data from HIV patients initiating first line antiretroviral therapy (ART) at the Infectious Diseases Institute (IDI) (Routine Cohort) was used. Three methods to estimate mortality after initiation were: 1) standard Kaplan-Meier estimation (uncorrected method) that uses passively observed data; 2) double-sampling methods by Frangakis and Rubin (F&R) where deaths obtained from patient tracing studies are given a higher weight than those passively ascertained; 3) Nomogram proposed by Egger et al. Corrected mortality estimates in the Routine Cohort, were compared with the estimates from the IDI research observational cohort (Research Cohort), which was used as the "gold-standard".
  
  
  RESULTS
  We included 5,633 patients from the Routine Cohort and 559 from the Research Cohort. Uncorrected mortality estimates (95% confidence interval [1]) in the Routine Cohort at 1, 2 and 3 years were 5.5% (4.9%-6.3%), 6.6% (5.9%-7.5%) and 7.4% (6.5%-8.5%), respectively. The F&R corrected estimates at 1, 2 and 3 years were 11.2% (5.8%-21.2%), 15.8% (9.9%-24.8%) and 18.5% (12.3% -27.2%) respectively. The estimates obtained from the Research Cohort were 15.6% (12.8%-18.9%), 17.5% (14.6%-21.0%) and 19.0% (15.3%-21.9%) at 1, 2 and 3 years respectively. Using the nomogram method in the Routine Cohort, the corrected programme-level mortality estimate in year 1 was 11.9% (8.0%-15.7%).
  
  
  CONCLUSIONS
  Mortality adjustments provided by the F&R and nomogram methods are adequate and should be employed to correct mortality for loss-to-follow-up in large HIV care centres in Sub-Saharan Africa.
authors.affiliation: Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda.
authors.forename: Agnes N
authors.initials: AN
authors.lastname: Kiragga
authors.affiliation: Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda.
authors.forename: Barbara
authors.initials: B
authors.lastname: Castelnuovo
authors.affiliation: Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda.
authors.forename: Rachel
authors.initials: R
authors.lastname: Musomba
authors.affiliation: Medical Research Council/Uganda Virus Research Institute Uganda Research Unit on AIDS, Entebbe, Uganda.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Levin
authors.affiliation: Infectious Diseases Institute, College of Health Sciences, Makerere University, Kampala, Uganda.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kambugu
authors.affiliation: School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Yukari C
authors.initials: YC
authors.lastname: Manabe
authors.affiliation: Indiana University Richard M. Fairbanks School of Public Health, Department of Biostatistics, Indianapolis, Indiana, United States of America.
authors.forename: Constantin T
authors.initials: CT
authors.lastname: Yiannoutsos
authors.affiliation: School of Public Health, College of Health Sciences, Makerere University Kampala, Uganda.
authors.forename: Noah
authors.initials: N
authors.lastname: Kiwanuka
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000188:drug therapy* / Q000401:mortality*; D006801:Humans; D053208:Kaplan-Meier Estimate; D059012:Lost to Follow-Up; D008297:Male; D014454:Uganda / Q000453:epidemiology
chemical_list: D019380:Anti-HIV Agents