title: Validation of a clinical-radiographic score to assess the probability of pulmonary tuberculosis in suspect patients with negative sputum smears.
abstract: BACKGROUND
  Clinical suspects of pulmonary tuberculosis in which the sputum smears are negative for acid fast bacilli represent a diagnostic challenge in resource constrained settings. Our objective was to validate an existing clinical-radiographic score that assessed the probability of smear-negative pulmonary tuberculosis (SNPT) in high incidence settings in Peru.
  
  
  RESULTS
  We included in two referral hospitals in Lima patients with clinical suspicion of pulmonary tuberculosis and two or more negative sputum smears. Using a published but not externally validated score, patients were classified as having low, intermediate or high probability of pulmonary tuberculosis. The reference standard for the diagnosis of tuberculosis was a positive sputum culture in at least one of 2 liquid (MGIT or Middlebrook 7H9) and 1 solid (Ogawa) media. Prevalence of tuberculosis was calculated in each of the three probability groups. 684 patients were included. 184 (27.8%) had a diagnosis of pulmonary tuberculosis. The score did not perform well in patients with a previous history of pulmonary tuberculosis. In patients without, the prevalence of tuberculosis was 5.1%, 31.7% and 72% in the low, intermediate and high probability group respectively. The area under de ROC curve was 0.76 (95% CI 0.72-0.80) and scores ≥6 had a positive LR of 10.9.
  
  
  CONCLUSIONS
  In smear negative suspects without previous history of tuberculosis, the clinical-radiographic score can be used as a tool to assess the probability of pulmonary tuberculosis and to guide the decision to initiate or defer treatment or to requesting additional tests.
authors.affiliation: Department of Medicine, Hospital Nacional Hipólito Unanue, Lima, Peru. sotosolari@yahoo.com
authors.forename: Alonso
authors.initials: A
authors.lastname: Soto
authors.forename: Lely
authors.initials: L
authors.lastname: Solari
authors.forename: Javier
authors.initials: J
authors.lastname: Díaz
authors.forename: Alberto
authors.initials: A
authors.lastname: Mantilla
authors.forename: Francine
authors.initials: F
authors.lastname: Matthys
authors.forename: Patrick
authors.initials: P
authors.lastname: van der Stuyft
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D015203:Reproducibility of Results; D013183:Sputum / Q000382:microbiology; D014057:Tomography, X-Ray Computed; D014397:Tuberculosis, Pulmonary / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000382:microbiology