title: Evaluation of three sampling methods to monitor outcomes of antiretroviral treatment programmes in low- and middle-income countries.
abstract: BACKGROUND
  Retention of patients on antiretroviral therapy (ART) over time is a proxy for quality of care and an outcome indicator to monitor ART programs. Using existing databases (Antiretroviral in Lower Income Countries of the International Databases to Evaluate AIDS and Médecins Sans Frontières), we evaluated three sampling approaches to simplify the generation of outcome indicators.
  
  
  RESULTS
  We used individual patient data from 27 ART sites and included 27,201 ART-naive adults (≥15 years) who initiated ART in 2005. For each site, we generated two outcome indicators at 12 months, retention on ART and proportion of patients lost to follow-up (LFU), first using all patient data and then within a smaller group of patients selected using three sampling methods (random, systematic and consecutive sampling). For each method and each site, 500 samples were generated, and the average result was compared with the unsampled value. The 95% sampling distribution (SD) was expressed as the 2.5(th) and 97.5(th) percentile values from the 500 samples. Overall, retention on ART was 76.5% (range 58.9-88.6) and the proportion of patients LFU, 13.5% (range 0.8-31.9). Estimates of retention from sampling (n = 5696) were 76.5% (SD 75.4-77.7) for random, 76.5% (75.3-77.5) for systematic and 76.0% (74.1-78.2) for the consecutive method. Estimates for the proportion of patients LFU were 13.5% (12.6-14.5), 13.5% (12.6-14.3) and 14.0% (12.5-15.5), respectively. With consecutive sampling, 50% of sites had SD within ±5% of the unsampled site value.
  
  
  CONCLUSIONS
  Our results suggest that random, systematic or consecutive sampling methods are feasible for monitoring ART indicators at national level. However, sampling may not produce precise estimates in some sites.
authors.affiliation: Department of HIV/AIDS, World Health Organisation, Geneva, Switzerland. tassiej@who.int
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Tassie
authors.forename: Karen
authors.initials: K
authors.lastname: Malateste
authors.forename: Mar
authors.initials: M
authors.lastname: Pujades-Rodríguez
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Poulet
authors.forename: Diane
authors.initials: D
authors.lastname: Bennett
authors.forename: Anthony
authors.initials: A
authors.lastname: Harries
authors.forename: Mary
authors.initials: M
authors.lastname: Mahy
authors.forename: Mauro
authors.initials: M
authors.lastname: Schechter
authors.forename: Yves
authors.initials: Y
authors.lastname: Souteyrand
authors.forename: François
authors.initials: F
authors.lastname: Dabis
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy* / Q000401:mortality / Q000821:virology; D000328:Adult; D017954:Africa South of the Sahara; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D002160:Cambodia; D003906:Developing Countries; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D007194:India; D059012:Lost to Follow-Up; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000706:statistics & numerical data; D010349:Patient Compliance / Q000706:statistics & numerical data; D010352:Patient Dropouts / Q000706:statistics & numerical data; D015397:Program Evaluation / Q000379:methods* / Q000706:statistics & numerical data; D015996:Survival Rate; D013997:Time Factors
chemical_list: D019380:Anti-HIV Agents