title: Improved diagnosis of Ziehl-Neelsen smear negative tuberculosis using sodium hypochlorite sedimentation method.
abstract: BACKGROUND
  Bacteriological diagnosis of tuberculosis (TB) is largely dependent on Ziehl-Neelsen (ZN) microscopy. This method has a low sensitivity. Although concentration of sputum with sodium hypochlorite (NaOC1) followed by sedimentation increases the sensitivity of direct smear microscopy, no study has focused on the effect of NaOC1 on smear negative sputum specimens.
  
  
  OBJECTIVE
  To establish whether 3.5% NaOC1 sedimentation method specifically improves the diagnosis of Ziehl-Neelsen smear negative tuberculosis.
  
  
  METHODS
  A prospective study.
  
  
  METHODS
  Mbagathi District Hospital and Center for Respiratory Diseases Research, Kenya Medical Research Institute.
  
  
  METHODS
  Two hundred and thirty confirmed direct ZN smear negative sputum specimens from new TB suspects were analysed.
  
  
  RESULTS
  Seventy (30.4%) specimens were culture positive. Of these, 19 were ZN smear positive. The ZN sensitivity, specificity, positive and negative predictive values were 27.1%, 99%, 95% and 76%, respectively, after sedimentation with 3.5% NaOC1.
  
  
  CONCLUSIONS
  Overnight sedimentation using 3.5% NaOC1 significantly improves diagnosis of ZN smear negative TB. This technique has potential to improve diagnosis in TB diagnostic services especially in settings with high burden of dual TB/HIV infection.
authors.affiliation: Centre for Respiratory Diseases Research, Kenya Medical Research Institute, P.O. Box 47855, Nairobi, Kenya.
authors.forename: W A
authors.initials: WA
authors.lastname: Githui
authors.forename: S W
authors.initials: SW
authors.lastname: Matu
authors.forename: L N
authors.initials: LN
authors.lastname: Muthami
authors.forename: E
authors.initials: E
authors.lastname: Juma
mesh_terms: D019411:Clinical Laboratory Techniques; D006801:Humans; D011446:Prospective Studies; D012973:Sodium Hypochlorite; D013997:Time Factors; D014376:Tuberculosis / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D012973:Sodium Hypochlorite