Acid fast bacilli in aspiration smears from tuberculous patients

Fine-Needle aspiration (FNA) has been used in the diagnosis of tuberculous adenitis or extrapulmonary tuberculosis of extranodal sites for more than ten years in the Tikur Anbessa Teaching Hospital, Department of Pathology, Faculty of Medicine, Addis Ababa University. The purpose of this study was to see the correlation between the cytomorphologic diagnosis and the subsequent demonstration of acid fast bacilli in the smear and also to know the overall acid fast bacilli (AFB) positivity. A cross sectional study, involving a total of 205 consecutive patients diagnosed to have tuberculosis by cytomorphology (FNA) between mid 1996 and early 1997 were included in the study. The May-Grunwald Giemsa stained smears were classified into three categories: Epithelioid granuloma without caseous necrosis, Epithelioid granuloma with caseous necrosis, Abscess and/or Caseous necrosis. There were 131 (63.9%) cases with granuloma with caseous necrosis, 67(32.7%) cases with abscess and/or caseous necrosis , and only seven (3.4%) cases with granuloma without caseous necrosis. The AFB positivity as stained by Ziehl Neelsen stain was 99 (75.6%) in granuloma with caseous necrosis, 46(68.7%) in tuberculous abscess and/or caseous necrosis and 2(28.5%) in granuloma without necrosis. The overall acid fast positivity was 71.7%. This study confirmed that FNA alone is helpful enough in making a diagnosis of tuberculosis in most of the cases. We recommend that the evaluation of all fine needle aspiration samples from suspected cases of tuberculosis should include staining for AFB for confirmation and in particular for cases of abscess and necrosis as part a diagnostic step. However, culture of the aspirate is still required when the smears are AFB negative and cytologically equivocal whenever it is available. (Ethiopian Journal of Health Development: 2000, 14(1): 99-104)