title: Impact of probability estimation on frequency of urine culture requests in ambulatory settings.
abstract: OBJECTIVE
  To determine the perceptions of the medical community about urine culture in diagnosing urinary tract infections.
  
  
  METHODS
  The cross-sectional survey based of consecutive sampling was conducted at Shifa International Hospital, Islamabad, on 200 doctors, including medical students of the Shifa College of Medicine, from April to October 2010. A questionnaire with three common clinical scenarios of low, intermediate and high pre-test probability for urinary tract infection was used to assess the behaviour of the respondents to make a decision for urine culture test. The differences between the reference estimates and the respondents' estimates of pre- and post-test probability were assessed. The association of estimated probabilities with the number of tests ordered was also evaluated. The respondents were also asked about the cost effectiveness and safety of urine culture and sensitivity. Data was analysed using SPSS version 15.
  
  
  RESULTS
  In low pre-test probability settings, the disease probability was over-estimated, suggesting the participants' inability to rule out the disease. The post-test probabilities were, however, under-estimated by the doctors as compared to the students. In intermediate and high pre-test probability settings, both over- and underestimation of probabilities were noticed. Doctors were more likely to consider ordering the test as the disease probability increased. Most of the respondents were of the opinion that urine culture was a cost-effective test and there was no associated potential harm.
  
  
  CONCLUSIONS
  The wide variation in the clinical use of urine culture necessitates the formulation of appropriate guidelines for the diagnostic use of urine culture, and application of Bayesian probabilistic thinking to real clinical situations.
authors.affiliation: Department of Medicine, Shifa College of Medicine, Islamabad, Pakistan. doctornaheed@live.com
authors.forename: Naheed
authors.initials: N
authors.lastname: Gul
authors.forename: Mujtaba
authors.initials: M
authors.lastname: Quadri
mesh_terms: D000328:Adult; D000553:Ambulatory Care; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011336:Probability; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D016482:Urinalysis; D014552:Urinary Tract Infections / Q000175:diagnosis* / Q000382:microbiology