title: Tuberculin skin test: estimation of positive and negative predictive values from routine data.
abstract: OBJECTIVE
  To estimate, using routinely available data, the predictive values of tuberculin testing with 2TU RT23 for detection of latent tuberculosis infection (LTBI) in the Dutch population as a basis for recommendations on cut-off values at various levels of infection prevalence.
  
  
  METHODS
  Smoothed distributions of TST reactions among 312 tuberculosis patients and 2848 healthy non-BCG-vaccinated persons were used to estimate the sensitivity and specificity at various cut-off values.
  
  
  RESULTS
  Sensitivity was 98.9% at 5 mm, 95.4% at 10 mm and 79.8% at 15 mm cut-off. Specificity with the corresponding cut-offs was 95.3%, 96.3% and 97.1% before and 98.0%, 98.8% and 99.6% after adjustment for presumed LTBI. At 10 mm, the positive predictive value (PPV) was > 75% if the infection prevalence in the tested population was at least 10%, but strongly declined with lower prevalences. For lower prevalences a cut-off of 15 mm was proposed, as this results in a higher PPV without greatly affecting the negative predictive value.
  
  
  CONCLUSIONS
  Estimation of the predictive values of the TST from routine data can be useful for establishing cut-off values for detection of LTBI in different populations with different tuberculin preparations.
authors.affiliation: Tuberculosis Control, GGD Hart voor Brabant, 's Hertogenbosch, The Netherlands.
authors.forename: G M
authors.initials: GM
authors.lastname: Berkel
authors.forename: F G J
authors.initials: FG
authors.lastname: Cobelens
authors.forename: G
authors.initials: G
authors.lastname: de Vries
authors.forename: I W E
authors.initials: IW
authors.lastname: Draayer-Jansen
authors.forename: M W
authors.initials: MW
authors.lastname: Borgdorff
mesh_terms: D000328:Adult; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D016008:Statistical Distributions; D014374:Tuberculin Test / Q000592:standards / Q000706:statistics & numerical data*; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology