Detection of tubercle bacilli in sputum: application of sodium hypochlorite concentration method

Tuberculosis has emerged as the leading cause of death due to single infectious agent. Sputum microscopy forms mainstay of diagnosis as it is most reliable, specific and objective method available especially in developing countries. However, this method is hampered by lack of sensitivity. Liquefaction and concentration of sputum before Ziehl Neelsen staining improves yield and also makes examination of smears rapid and convenient. A total of 304 sputum samples were studied by direct staining and after sodium hypochlorite treatment and centrifugation. Direct smears stained with Auramine-Phenol were also examined. Use of sodium hypochlorite method increased the number of positive samples from 52 to 96. No false positives were detected by either method. The method is simple as the only extra reagent required is sodium hypochlorite that is easily available. Additional advantage is that sodium hypochlorite, being a potent disinfectant, reduces the risk of laboratory acquired infections.