title: Adolescent condom use consistency over time: global versus partner-specific measures.
abstract: BACKGROUND
  The conundrum of measuring condom use consistency, particularly with adolescents, has left researchers with a cacophony of strategies, thereby limiting comparability and interpretation.
  
  
  OBJECTIVE
  The aim of this analysis was to compare and contrast two measures of condom use consistency, global versus partner specific, and their relationships with key covariates, using trajectory groups differentiated by stability of condom use consistency over three time points.
  
  
  METHODS
  Using self-report data from sexually active girls (aged 13-17 years) in a clinic-based intervention study aimed at lowering risk for early pregnancy, this analysis compared two measures of self-reported condom use consistency: (a) a global measure: overall condom use consistency in the past 6 months and (b) a partner-specific measure: condom use consistency with the most recent sex partner in the last 6 months. Using a subjective rule-based approach, the adolescent girls in the study (n = 151) were classified into trajectory groups representing their condom use consistency at three time points (baseline and 6 and 12 months). Then, using bivariate methods, trajectory groups were compared on four baseline covariates (age, treatment condition, hormonal use in the last 6 months, and number of sex partners in the last 6 months) and three time-varying covariates measured at baseline and at 6 and 12 months (hormonal use stability, stability of primary sex partner, and stability of number of sex partners).
  
  
  RESULTS
  For the trajectory groups formed using the global measure of condom use consistency, stability of the primary sex partner differed significantly between trajectory groups. For the partner-specific trajectory groups, two baseline and one time-varying covariate relationships were significant: hormonal use in the 6 months prior to baseline, number of sex partners in the past 6 months (baseline), and stability of the primary sex partner (time varying), with hormonal use stability (time varying) trending toward significance.
  
  
  CONCLUSIONS
  The larger number of significant covariate relationships with the partner-specific trajectory groups suggests greater utility in assessing partner-linked behavior rather than a global measure. Despite limitations of the analytic strategy, this study sheds light on a measurement conundrum that has been an obstacle to comparing and contrasting indicators of condom use consistency during adolescence.
authors.affiliation: School of Nursing and Department of Pediatrics, Medical School, Minneapolis, Minneapolis, MN 55455, USA. beari001@umn.edu
authors.forename: Linda H
authors.initials: LH
authors.lastname: Bearinger
authors.forename: Renee E
authors.initials: RE
authors.lastname: Sieving
authors.forename: Naomi N
authors.initials: NN
authors.lastname: Duke
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: McMorris
authors.forename: Sarah
authors.initials: S
authors.lastname: Stoddard
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Pettingell
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000367:Age Factors; D017280:Condoms / Q000706:statistics & numerical data*; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D012737:Sex Factors; D012725:Sexual Behavior / Q000523:psychology*; D012747:Sexual Partners; D013997:Time Factors