title: Co-calibration of two self-reported measures of adherence to antiretroviral therapy.
abstract: Adherence to antiretroviral therapy (ART) is an important determinant of clinical success assessed in many HIV studies. Harmonizing adherence data from studies that use different measures is difficult without a co-calibration equation to convert between validated instruments. Our purpose was to co-calibrate two commonly used adherence measures: the AIDS Clinical Trials Group (ACTG) questionnaire and the Visual Analog Scale (VAS). We used robust linear regression to develop a co-calibration equation in a clinical care cohort. The outcome was the 30-day VAS percentage of ART taken and the predictors were ACTG questions. We evaluated the equation's goodness of fit in five STTR (Seek, Test, Treat, Retain) consortium studies where individuals completed both measures: 2 criminal justice; 2 international; and 1 other high-risk vulnerable population. We developed a three-phase decision rule to convert ACTG to VAS in 1045 participants. First, when the last missed dose on the ACTG was reported as >30 days ago, the VAS was set to 100% (N = 582). Second, if "doses missed" was zero for all items, VAS was 100% (N = 104). Third, among remaining participants (N = 359), VAS was estimated as 96.8% minus 2.9% times the number of missed doses ("doses per day" was non-significant). Correlation between predicted and reported VAS was r = 0.80 in the criminal justice group (N = 446), r = 0.46 in the international group (N = 311), r = 0.32 in the other vulnerable population (N = 63), and r = 0.66 overall. When outliers due to inversion of the VAS scale were excluded (n = 25), these correlations were 0.88, 0.78, 0.80, and 0.86, respectively. We concluded that a simple decision rule and equation allowed us to co-calibrate between two widely used adherence measures thus combining data from studies with different instruments. This study highlighted issues with VAS inversions and its limitations as a single item. Combining studies using different instrument facilitates larger pooled datasets to address key research questions.
authors.affiliation: a Department of Medicine , University of Washington , Seattle , WA , USA.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Nance
authors.affiliation: b Department of Epidemiology , University of Washington , Seattle , WA , USA.
authors.forename: J A Chris
authors.initials: JA
authors.lastname: Delaney
authors.affiliation: c Department of Medicine , University of North Carolina at Chapel Hill , Chapel Hill , NC , USA.
authors.forename: Carol E
authors.initials: CE
authors.lastname: Golin
authors.affiliation: d RTI Global Gender Center, RTI International , RTP , NC , USA.
authors.forename: Wendee M
authors.initials: WM
authors.lastname: Wechsberg
authors.affiliation: e Division of General Internal Medicine , Albert Einstein College of Medicine/Montefiore Medical Center , Bronx , NY , USA.
authors.forename: Chinazo
authors.initials: C
authors.lastname: Cunningham
authors.affiliation: f Department of Medicine, Yale University School of Medicine , New Haven , CT , USA.
authors.forename: Frederick
authors.initials: F
authors.lastname: Altice
authors.affiliation: g Department of Medicine , University of California , San Francisco , CA , USA.
authors.forename: Katerina
authors.initials: K
authors.lastname: Christopoulos
authors.affiliation: h Institute of Behavioral Research, Texas Christian University , Fort Worth , TX , USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Knight
authors.affiliation: i Department of Epidemiology , Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA.
authors.forename: Vu
authors.initials: V
authors.lastname: Quan
authors.affiliation: j Friends Research Institute, Inc. , Baltimore , MD , USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Gordon
authors.affiliation: k Department of Medicine , Yale School of Medicine , New Haven , CT , USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: Springer
authors.affiliation: l Department of Medicine , University of Illinois at Chicago , Chicago , IL , USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Young
authors.affiliation: a Department of Medicine , University of Washington , Seattle , WA , USA.
authors.forename: Paul K
authors.initials: PK
authors.lastname: Crane
authors.affiliation: m The Fenway Institute , Boston , MA , USA.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Mayer
authors.affiliation: n Department of Medicine , University of Alabama , Birmingham , AL , USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mugavero
authors.affiliation: o Department of Medicine , Emory/Rollins School of Public Health , Atlanta , GA , USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Del Rio
authors.affiliation: b Department of Epidemiology , University of Washington , Seattle , WA , USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Kronmal
authors.affiliation: a Department of Medicine , University of Washington , Seattle , WA , USA.
authors.forename: Heidi M
authors.initials: HM
authors.lastname: Crane
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D002138:Calibration; D005260:Female; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D057566:Self Report; D011795:Surveys and Questionnaires; D064232:Visual Analog Scale; D016903:Drug Monitoring
chemical_list: D019380:Anti-HIV Agents
keywords: Adherence; HIV; antiretroviral therapy; calibration; visual analog scale