title: Confidence in polymerase chain reaction diagnosis can be improved by Bayesian estimation of post-test disease probability.
abstract: OBJECTIVE
  Polymerase chain reaction (PCR) techniques allow highly sensitive detection of specific DNA for diagnosis of infectious and genetic disease, but uncertainty relating to sensitivity and contamination has frequently resulted in controversy over results. We propose a new design in which the PCR contamination rate is estimated experimentally. The sensitivity of duplicate test results, and hence the post-test disease probabilities, can be derived algebraically, but wide confidence limits around these point estimates reduce their usefulness.
  
  
  METHODS
  We have developed a Bayesian method which gives better estimates of post-test disease probability and can substantially reduce uncertainty by using the prior belief that sensitivity is not lower than 90%.
  
  
  RESULTS
  With 100 duplicate test samples and 100 control samples, we find that the post-test disease probability for concordant results (both positive or both negative) is generally unequivocal. The post-test disease probability for discordant results (one test positive and one negative) is often sufficiently clear to allow useful interpretation of individual test results, depending on the context.
  
  
  CONCLUSIONS
  Using this approach, the performance of a PCR can be evaluated experimentally allowing post-test disease probability to be estimated, giving improved confidence in test results.
authors.affiliation: Institute of Cell and Molecular Science, St. Bartholomew's & the Royal London School of Medicine and Dentistry, Turner Street, London E1 2AD, UK. m.p.kelly@qmul.ac.uk
authors.forename: Paul
authors.initials: P
authors.lastname: Kelly
authors.forename: Filomena
authors.initials: F
authors.lastname: Pereira-Maxwell
authors.forename: Simon
authors.initials: S
authors.lastname: Carnaby
authors.forename: Ian
authors.initials: I
authors.lastname: White
mesh_terms: D001499:Bayes Theorem; D004866:Equipment Contamination; D006801:Humans; D015233:Models, Statistical; D016133:Polymerase Chain Reaction / Q000592:standards*; D011237:Predictive Value of Tests; D012107:Research Design; D012680:Sensitivity and Specificity