title: Might ART Adherence Estimates Be Improved by Combining Biomarker and Self-Report Data?
abstract: BACKGROUND
  As we endeavour to examine rates of viral suppression in PLHIV, reliable data on ART adherence are needed to distinguish between the respective contributions of poor adherence and treatment failure on high viral load. Self-reported data are susceptible to response bias and although biomarker data on drug presence and concentration can provide a superior, alternative method of measurement, complications due to drug-drug interactions and genetic variations can cause some inaccuracies. We investigate the feasibility of combining both biomarker and self-report data to produce a potentially more accurate measure of ART adherence.
  
  
  METHODS
  Data were taken from a large general-population survey in the Manicaland province, Zimbabwe, conducted in 2009-2011. HIV-infected adults who had initiated ART (N = 560) provided self-report data on adherence and dried blood spot samples that were analysed for traces of ART medication. A new three-category measure of ART adherence was constructed, based on biomarker data but using self-report data to adjust for cases with abnormally low and high drug concentrations due to possible drug-drug interactions and genetic factors, and was assessed for plausibility using survey data on socio-demographic correlates.
  
  
  RESULTS
  94.3% (528/560) and 92.7% (519/560) of the sample reported faithful adherence to their medication and had traces of ART medication, respectively. The combined measure estimated good evidence of ART adherence at 69% and excellent evidence of adherence at 53%. The regression analysis results showed plausible patterns of ART adherence by socio-demographic status with men and younger participants being more likely to adhere poorly to medication, and higher socio-economic status individuals and those living in more urban locations being more likely to adhere well.
  
  
  CONCLUSIONS
  Biomarker and self-reported measures of adherence can be combined in a meaningful way to produce a potentially more accurate measure of ART adherence. Results indicate that ART adherence in Manicaland is at best 69%, which not only allows for considerable room for improvement but also suggests that the area may be falling short of the UNAIDS' 90% target regarding viral suppression. Increased efforts are needed to improve ART adherence particularly amongst the young male population in rural areas of east Zimbabwe.
authors.affiliation: Imperial College London, Department of Infectious Disease Epidemiology, London, United Kingdom.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Rhead
authors.affiliation: African Institute of Biomedical Research and Technology, Harare, Zimbabwe.
authors.forename: Collen
authors.initials: C
authors.lastname: Masimirembwa
authors.affiliation: Imperial College London, Department of Medicine, London, United Kingdom.
authors.forename: Graham
authors.initials: G
authors.lastname: Cooke
authors.affiliation: Biomedical Research and Training Institute, Harare, Zimbabwe.
authors.forename: Albert
authors.initials: A
authors.lastname: Takaruza
authors.affiliation: Biomedical Research and Training Institute, Harare, Zimbabwe.
authors.forename: Constance
authors.initials: C
authors.lastname: Nyamukapa
authors.affiliation: African Institute of Biomedical Research and Technology, Harare, Zimbabwe.
authors.forename: Cosmas
authors.initials: C
authors.lastname: Mutsimhi
authors.affiliation: Imperial College London, Department of Infectious Disease Epidemiology, London, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Gregson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D015415:Biomarkers / Q000032:analysis*; D004347:Drug Interactions; D005260:Female; D014644:Genetic Variation; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D057566:Self Report; D016896:Treatment Outcome; D019562:Viral Load; D055815:Young Adult; D015030:Zimbabwe; D016903:Drug Monitoring
chemical_list: D019380:Anti-HIV Agents; D015415:Biomarkers