title: Impact of definitions of loss to follow-up on estimates of retention, disease progression, and mortality: application to an HIV program in Mozambique.
abstract: Patient retention is critical to the management of chronic diseases such as human immunodeficiency virus (HIV); hence, accurate measures of loss to follow-up (LTF) are important. Many different LTF definitions have been proposed. In a cohort of 9,692 HIV-infected patients initiating antiretroviral therapy in Mozambique from 2006 to 2011, we investigated the impact of the definition of LTF on estimated rates of LTF, acquired immunodeficiency syndrome (AIDS)-defining events, and death by applying 17 different definitions of LTF gleaned from HIV literature. We further investigated the impact of 4 specific components of the LTF definitions. Cumulative incidences of LTF and AIDS-defining events were estimated by treating death as a competing risk; Kaplan-Meier techniques and variations to account for informative censoring were used to estimate rates of mortality. Estimates of LTF 2 years after treatment initiation were high and varied substantially, from 22% to 84% depending on the LTF definition used. Estimates of 2-year mortality varied from 11% to 16%, and estimates of 2-year AIDS-defining events varied from 6% to 8%. As seen here, the choice of LTF definition can greatly affect study conclusions and program evaluations. Selection of LTF definitions should be based on the study outcome, available data on clinical encounters, and the patients' visit schedules; we suggest some general guidelines.
authors.affiliation: Vanderbilt University School of Medicine, 1161 21st Avenue South, Nashville,TN 37232-2158, USA. bryan.shepherd@vanderbilt.edu
authors.forename: Bryan E
authors.initials: BE
authors.lastname: Shepherd
authors.forename: Meridith
authors.initials: M
authors.lastname: Blevins
authors.forename: Lara M E
authors.initials: LM
authors.lastname: Vaz
authors.forename: Troy D
authors.initials: TD
authors.lastname: Moon
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Kipp
authors.forename: Eurico
authors.initials: E
authors.lastname: José
authors.forename: Ferreira G
authors.initials: FG
authors.lastname: Ferreira
authors.forename: Sten H
authors.initials: SH
authors.lastname: Vermund
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy / Q000453:epidemiology; D000328:Adult; D044966:Anti-Retroviral Agents / Q000627:therapeutic use; D003625:Data Collection / Q000379:methods; D003627:Data Interpretation, Statistical; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000401:mortality; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D009073:Mozambique / Q000453:epidemiology; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data; D012107:Research Design; D013997:Time Factors
chemical_list: D044966:Anti-Retroviral Agents
keywords: HIV; chronic disease; cohort studies; long-term care; lost to follow-up; program evaluation