Role of sputum examination for acid fast bacilli in tuberculous pleural effusion

Sputum for acid fast bacilli (AFB) is seldom looked for in the etiological diagnosis of tuberculous pleural effusion usually due to the absence of any parenchymal lesion radiologically, but presence of tubercle bacilli in sputum may have important epidemiological and therapeutic implication.

This study aims to evaluate the role of sputum examination for AFB in the patients of tuberculous pleural effusion with no apparent lung parenchymal lesion radiologically.

Forty-five consecutive indoor patients of suspected tuberculous pleural effusion having no apparent lung parenchymal lesion on chest radiography were selected for our study. It was a prospective and observational study conducted over a period of 1 year.

After confirming the etiology of pleural effusion as tuberculous by biochemical, cytological, histopahtological, and microbiological tests, emphasis was given on sputum examination for AFB by smear examination and culture for Mycobacterium tuberculosis.

Sputum was bacteriologically (smear and /or culture) positive for tuberculosis in 10 out of 30 cases (33.33%) in which tuberculous etiology was confirmed by histology and /or bacteriology (definite tuberculosis). No sputum AFB (smear and culture) was found in 15 cases of probable tuberculosis where tuberculous etiology was established by indirect methods like Adenosine de aminase level more than 40 unit/l and other relevant investigations. Over all, sputum was bacteriologically smear and/or culture positive in 10 out of 45 cases (22.22%).

Careful and thorough sputum examination in cases of tuberculous pleural effusion may help as a diagnostic tool and it has therapeutic and epidemiological implications.