title: Adequacy of two versus three sputum specimens for the diagnosis of pulmonary tuberculosis.
abstract: BACKGROUND
  The new guidelines issued by the Revised National Tuberculosis Control Programme for diagnosis of smear-positive tuberculosis recommend examination of only 2 sputum smears. We did a retrospective analysis of data from a designated microscopy centre to ascertain the diagnostic yield of 2 smears and the additional yield provided by the third smear.
  
  
  METHODS
  Data were obtained from the designated microscopy centre attached to our medical college. A total of 3257 patients with suspected tuberculosis had undergone sputum examination between September 2004 and March 2009. However, only 1762 of them had 3 sputum specimens examined. Data were entered and analysed using SPSS version 11.5.
  
  
  RESULTS
  Among the 1762 suspected patients, positivity in any 2 samples was found to be 17.7% while 19% were found to be positive in a single smear. A statistically insignificant association was found between the grading and positivity of the sputum samples using McNemar test. A positive third sample was found in 309 patients. If the first 2 samples were negative, the possibility of missing a third positive sample was 0.4%.
  
  
  CONCLUSIONS
  Under field conditions, 2 sputum smears are as effective as 3 smears for diagnosing smear-positive tuberculosis.
authors.affiliation: Department of Community Medicine, Kasturba Medical College, Manipal University, Manipal 576104, Karnataka, India. drashwiniin@hotmail.com
authors.forename: Ashwini
authors.initials: A
authors.lastname: Kumar
authors.forename: Indira
authors.initials: I
authors.lastname: Bairy
authors.forename: Chythra R
authors.initials: CR
authors.lastname: Rao
authors.forename: Vishnu
authors.initials: V
authors.lastname: Prasad
authors.forename: Sanjay
authors.initials: S
authors.lastname: Pattanshetty
authors.forename: Charmaine Minoli
authors.initials: CM
authors.lastname: Samarasinghe
mesh_terms: D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*