title: Evaluation of combined LED-fluorescence microscopy and bleach sedimentation for diagnosis of tuberculosis at peripheral health service level.
abstract: BACKGROUND
  Sputum microscopy is the only diagnostic for tuberculosis (TB) available at peripheral levels of health service in resource-poor countries. Its sensitivity is reduced in high HIV-prevalence settings. Sodium hypochlorite (NaOCl) specimen sedimentation prior microscopy and light-emitting diode (LED)-fluorescence microscopy (FM) can individually improve performance of microscopy. This study aimed to evaluate the performance of combined LED-FM and NaOCl sputum sedimentation for TB detection at peripheral level of health services.
  
  
  METHODS
  A prospective study was conducted in an urban health clinic in Nairobi, Kenya. Three sputum specimens were collected over 2 days from consecutive TB suspects. Smears were prepared and stained with auramine O and Ziehl-Neelsen (ZN) methods. Bleach (3.5%) was added to the remaining specimen before overnight sedimentation at room temperature. Auramine O staining was performed on smears of sediment. A 4(th) specimen was collected for TB culture. Auramine smears were read under the same microscope as used for ZN smears, but equipped with the LED FluoLED™ fluorescence illuminator.
  
  
  RESULTS
  497 patients were included, and 1394 specimens collected. The yield of positive specimen was significantly increased after NaOCl sedimentation (24.9%) compared to direct LED-FM (20.6%) and direct ZN (20.3%). In detecting smear-positive patients, sensitivity was 78.5% for LED-FM after NaOCl sedimentation compared to 73.2% and 72.0% for direct LED-FM (P = 0.06) and direct ZN (P = 0.06), respectively. Specificity was 87.8% for LED-FM after NaOCl sedimentation compared to 96.7% and 95.9% for direct LED-FM (P<0.01) and direct ZN (P<0.01), respectively. Inter-reading agreement (kappa = 0.7) and technicians' acceptability were good.
  
  
  CONCLUSIONS
  NaOCl sedimentation did not improve the performance of LED-FM in the diagnosis of pulmonary TB at peripheral health service level.
authors.affiliation: Epicentre, Paris, France. maryline.bonnet@geneva.msf.org
authors.forename: Maryline
authors.initials: M
authors.lastname: Bonnet
authors.forename: Laramie
authors.initials: L
authors.lastname: Gagnidze
authors.forename: Philippe J
authors.initials: PJ
authors.lastname: Guerin
authors.forename: Laurence
authors.initials: L
authors.lastname: Bonte
authors.forename: Andrew
authors.initials: A
authors.lastname: Ramsay
authors.forename: Willie
authors.initials: W
authors.lastname: Githui
authors.forename: Francis
authors.initials: F
authors.lastname: Varaine
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods*; D008875:Middle Aged; D011446:Prospective Studies; D012973:Sodium Hypochlorite; D013048:Specimen Handling / Q000379:methods*; D014376:Tuberculosis / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D012973:Sodium Hypochlorite