Evaluation of bleach and phenol ammonium sulphate as sputum pretreatment methods for mycobacterium tuberculosis detection in suspected pulmonary tuberculosis patients

Introduction: Significant mortality and morbidity is caused by Tuberculosis (TB) in developing countries like India. Direct ZiehlNeelsen (ZN) sputum smear microscopy for the detection of AFB remains the most important diagnostic test for TB. But the sensitivity of this method in diagnosing pulmonary TB is discouragingly low. One approach to the improvement of sputum smear microscopy is the application of chemical pretreatment to disrupt sputum structure, separate clumps of mycobacteria, and concentrate bacilli, thereby increasing the probability of their detection. Aims and Objective: To compare the efficacy of Sodium Hypochlorite and Phenol ammonium sulphate pretreatment methods with direct sputum smear microscopy to detect AFB from sputum samples of suspected pulmonary TB patients. Methods: A total of 300 samples from 300 suspected pulmonary TB patients were studied. The sputum samples were divided into 3 parts and used for direct ZN staining, pretreatment with 5% sodium hypochlorite by centrifugation and sedimentation and phenol ammonium sulphate. The smears were stained by ZN technique and seen under 100 X oil immersion lens. The results were compared with culture on LJ media, as gold standard. Results: The sensitivity of direct microscopy was seen to be the lowest of 37.50%, followed by PhAS 45.83%, Bleach by sedimentation 50% and highest by Bleach by centrifugation method 52.08%. Conclusion: Pretreatment by sodium hypochlorite centrifugation method is a better method than PhAS for improving sputum smear microscopy.