Comparative Study of Direct Sputum Microscopy with Different Sample Pre-Treatment Procedures for Examination of Acid Fast Bacilli

Abstract

A comparative study of three methods of identifying Mycobacterium tuberculosis by microscopy was performed on the sputa of suspected pulmonary tuberculosis patients in Jimma Health Center from November 14 to December 6, 1998 Direct sputum microscopy was compared with microscopy after sodium hypochlorite pre-treatment overnight sedimentation and sodium hypochlorite pre-treatment overnight centrifugation techniques. One hundred sputum samples were examined for acid fast bacilli by direct microscopy, sodium hypochlorite overnight sedimentetion and hypochlorite centrifugation methods and gave 22 %, 37 % and 41 % sme: positivity respectively. The increment of positive results obtained by the two concentration methods over the direct method was statistically significant (P<0.05, X-8.36 and 3.41 for centrifugation and sedimentation methods respectively). The difference in the proportion of positive results obtained by the two concentration techniques was not statistically significant (P >0.05, 2 0.336). Therefore, employing a concentration method improves the efficiency of TB laboratories, and an overnight sedimentation method can be an alternative method for rural laboratories where there is no electric supply to use electrical centrifugation.