title: The rapid test paradox: when fewer cases detected lead to more cases treated: a decision analysis of tests for Chlamydia trachomatis.
abstract: OBJECTIVE
  Screening tests for detection of Chlamydia trachomatis include those processed in laboratories and those designed to be processed at the point of care. The latter tests can yield results at the time of the initial patient visit, but most available lab-processed tests have greater sensitivity. In settings where a proportion of patients do not return for treatment after positive test results, the less sensitive rapid tests could lead to the treatment of more patients and be more cost-effective.
  
  
  OBJECTIVE
  To determine the situations, if any, in which a rapid test might be more cost-effective and treat more infections than lab-based tests.
  
  
  METHODS
  A decision analysis framework was used to compare one point-of-care test (the BioStar Chlamydia OIA) with two lab-based tests (cell culture and the polymerase chain reaction [PCR] assay). It was assumed that all women in the model would be screened. Variables included in the analysis were the prevalence, test sensitivity and specificity, the probability of developing pelvic inflammatory disease after treated and untreated chlamydial infections, and the likelihood that patients would wait for rapid test results or return to the facility for treatment.
  
  
  RESULTS
  The rapid test treated more cases of infection than the PCR alone if the return rate was less than 65%. A two-test algorithm of the rapid test followed by a PCR test on those initially testing negative identified and treated the greatest number of chlamydial infections and was the most cost-effective at all prevalences above 9%, but this finding was sensitive to the cost estimate for pelvic inflammatory disease.
  
  
  CONCLUSIONS
  In settings where patient return for treatment is a problem, point-of-care tests contribute significantly to the detection and treatment of chlamydial infections among women.
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Gift
authors.forename: M S
authors.initials: MS
authors.lastname: Pate
authors.forename: E W
authors.initials: EW
authors.lastname: Hook
authors.forename: W J
authors.initials: WJ
authors.lastname: Kassler
mesh_terms: D002690:Chlamydia Infections / Q000175:diagnosis* / Q000188:drug therapy* / Q000191:economics; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D019411:Clinical Laboratory Techniques / Q000191:economics; D003362:Cost-Benefit Analysis; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D016133:Polymerase Chain Reaction; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D014481:United States
chemical_list: D011933:Reagent Kits, Diagnostic