title: Validation of bleach-treated smears for the diagnosis of pulmonary tuberculosis.
abstract: METHODS
  Health centres in Awassa, southern Ethiopia.
  
  
  METHODS
  Consecutive patients visiting health centre laboratories for the evaluation of suspected pulmonary tuberculosis (TB) between June and September 2006 were investigated. On-the-spot, morning and second on-the-spot sputum samples were pooled for each patient. Direct smears were stained with hot Ziehl-Neelsen (ZN) technique and aliquots cultured for mycobacteria on Löwenstein-Jensen media. The remaining sputum was treated with household bleach, aliquoted and processed with short-term digestion, centrifugation and sedimentation techniques, and stained with ZN.
  
  
  RESULTS
  Acid-fast bacilli were detected in respectively 126 (25%), 141 (28%), 169 (34%) and 198 (40%) of the 497 pooled sputum samples processed by the direct, short-term, sedimentation and centrifugation techniques (P < 0.001). The sensitivity of the direct, short-term, sedimentation and centrifugation techniques was respectively 51.1%, 53.2%, 57.6% and 63.6%. The difference between the direct smear and centrifugation (P < 0.001) or sedimentation (P < 0.005) methods was significant. The specificity of the direct, short-term digestion, sedimentation and centrifugation techniques was respectively 97%, 93%, 86.5% and 80.8%.
  
  
  CONCLUSIONS
  Bleach treatment of sputum and centrifugation significantly improves the sensitivity of smear microscopy for the diagnosis of TB in a health centre in a high TB burden area. It is more sensitive, but possibly less specific, than other bleach methods.
authors.affiliation: Armauer Hansen Research Institute, Addis Ababa, Ethiopia.
authors.forename: Y
authors.initials: Y
authors.lastname: Merid
authors.forename: M A
authors.initials: MA
authors.lastname: Yassin
authors.forename: L
authors.initials: L
authors.lastname: Yamuah
authors.forename: R
authors.initials: R
authors.lastname: Kumar
authors.forename: H
authors.initials: H
authors.lastname: Engers
authors.forename: A
authors.initials: A
authors.lastname: Aseffa
mesh_terms: D001431:Bacteriological Techniques; D002498:Centrifugation; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D012973:Sodium Hypochlorite; D013048:Specimen Handling / Q000379:methods*; D013183:Sputum / Q000382:microbiology*; D013194:Staining and Labeling; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*
chemical_list: D012973:Sodium Hypochlorite