IMPROVED DIAGNOSIS OF ZIEHL-NEELSEN SMEAR NEGATIVE TUBERCULOSIS USING SODIUM HYPOCHLORITE SEDIMENTATION METHOD

Abstract

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 (NaOCl) followed by sedimentation increases the sensitivity of direct smear
microscopy, no study has focused on the effect of NaOCl on smear negative sputum specimens.
Objective: To establish whether 3.5% NaOC1 sedimentation method specifi cally improves the
diagnosis of Ziehl-Neelsen smear negative tuberculosis.
Design: A prospective study.
Setting: Mbagathi District Hospital and Center for Respiratory Diseases Research, Kenya Medical
Research Institute.
Subjects: Two hundred and thirty confi rmed 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, specifi city, positive and negative predictive values were 27.1%, 99%, 95% and
76%, respectively, after sedimentation with 3.5% NaOC1.
Conclusion: Overnight sedimentation using 3.5% NaOC1 signifi cantly 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.