title: Treatment interruption and variation in tablet taking behaviour result in viral failure: a case-control study from Cape Town, South Africa.
abstract: BACKGROUND
  Understanding of the impact of non-structured treatment interruption (TI) and variation in tablet-taking on failure of first-line antiretroviral therapy (ART) is limited in a resource-poor setting.
  
  
  METHODS
  A retrospective matched case-control analysis. Individuals failing ART were matched by time on ART with 4 controls. Viral load (VL) and CD4 count were completed 4-monthly. Adherence percentages, from tablet returns, were calculated 4-monthly (interval) and from ART start (cumulative). Variation between intervals and TI (>27 days off ART) were recorded. Conditional multivariate logistic regression analysis was performed to estimate the effect of cumulative adherence <90%, at least one episode of adherence variation >10% and TI on virological failure. Age, gender, baseline log VL and CD4 were included as possible confounders in the multivariate model.
  
  
  RESULTS
  244 patients (44 cases, 200 controls) were included. Median age was 32 years (IQR28-37), baseline CD4 108 cells/mm3 (IQR56-151), VL 4.82 log (IQR4.48-5.23). 94% (96% controls, 86% failures) had cumulative adherence >90%. The odds of failure increased 3 times (aOR 3.01, 95%CI 0.81-11.21) in individuals with cumulative adherence <90%, 2.2 times (aOR 2.20, 95%CI 1.04-4.64) in individuals with at least one episode of fluctuating adherence of >10% and 4.01 times (aOR 4.01, 95%CI 1.45-11.10) in individuals with TIs. For individuals with TI and cumulative adherence >95%, the odds of failing were 5.65 (CI 1.40-22.85).
  
  
  CONCLUSIONS
  It is well known that poor cumulative adherence increases risk of virological failure, but less well understood that TI and variations in tablet-taking also play a key role, despite otherwise excellent adherence.
authors.affiliation: Desmond Tutu HIV Foundation, University of Cape Town, Cape Town, South Africa.
authors.forename: Lisa-Noelle
authors.initials: LN
authors.lastname: Ncaca
authors.forename: Katharina
authors.initials: K
authors.lastname: Kranzer
authors.forename: Catherine
authors.initials: C
authors.lastname: Orrell
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D023241:Antiretroviral Therapy, Highly Active; D018791:CD4 Lymphocyte Count / Q000706:statistics & numerical data; D016022:Case-Control Studies; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D016015:Logistic Models; D015999:Multivariate Analysis; D012189:Retrospective Studies; D013019:South Africa; D013607:Tablets; D017211:Treatment Failure; D019562:Viral Load / Q000706:statistics & numerical data; D016903:Drug Monitoring
chemical_list: D019380:Anti-HIV Agents; D013607:Tablets