Enhancement of yield of acid fast bacilli in smear negative sputum microscopy with sodium hypochlorite decontamination sedimentation technique

Introduction: To study usefulness of sodium hypochlorite (bleach) decontamination sedimentation technique to increase yield of acid fast bacilli (AFB) in sputum smear negative clinicoradiologically suspected pulmonary tuberculosis patients. Material & Methods: Cross-sectional prospective study conducted at department of Microbiology of a teaching hospital having RNTCP centre. Screening for AFB is routinely carried out at our RNTCP centre. Patients with 2 smears (spot & morning samples) were selected for study. Their clinicoradiological information & demographic details were collected. Out of 347 RNTCP registered patients (247 male & 100 Females) during Jan-Dec 2014, 49 (36 Males & 13 Females) (14.12%), AFB positive by RNTCP criteria. Rest of 298 smear negative, 255 included for study, 43 excluded because of salivary nature of sputum samples. Sputum negative smears were processed by Bleach sedimentation technique, left at room temperature for 4 hours. Supernatant discarded & smear prepared from sediment. Smears were heat fixed & Z-N staining done. Reporting done as per American Thoracic Society (ATS) grading. Result: Out of 255 patients, 26 were positive. Sensitivity increased by 10.19% (p value < 0.01). Conclusion: Smear positive cases significantly rises after sedimentation at room temperature for 4 hrs with bleach. Sputum pretreatment enhances yield of positive smears. Considering low cost, better sensitivity, liquefaction properties, poor power supply in remote areas, no need of centrifugation ( no aerosols), this method is safe and of vital importance for smear negative cases.