Improved method of direct microscopy for detection of acid-fast bacilli in sputum

Microscopy of direct smears for acid-fast bacilli (AFB) is the most commonly used method for diagnosis of tuberculosis. However, direct microscopy of sputum, though rapid, has low sensitivity and there is a need for improved methods. Sputum samples were collected from patients attending the Union Tuberculosis Institute, Yangon. The microscopy of smears made directly from sputum were compared with the microscopy after liquefaction of sputum with household bleach (NaOCl) and concentration of bacteria by centrifugation. Out of 948 samples, 248 samples (26.2%) were positive for acid-fast bacilli by direct microscopy and 293 samples (30.9%) were positive for acid-fast bacilli by the household bleach method. There was a significant increase in the number of acid-fast bacilli positive samples by the house-hold bleach method (p<0.05). The method is simple and cheap. As a disinfectant, household bleach has the advantage of lowering the risk of laboratory infection.