Detection of acid fast bacilli (AFB) in tuberculous lymphadenitis among adult Ethiopians.

BACKGROUND

The sensitivity of conventional methods used in mycobacteriology laboratories may not exceed 40% in extrapulmonary cases of tuberculosis. Fine needle aspiration cytology (FNAC) is the best and affordable alternative method of diagnosing tuberculous (TB) lymphadenitis. However detection of acid fast bacilli (AFB) remains the corner stone of confirming diagnosis of TB.

OBJECTIVES

To investigate the detection rate of AFB in FNAC specimens using the Ziehl Neelsen staining method and see if bacillary detection depends on cytomorphologic features of inflammation.

METHODS

All consecutive adult patients having solitary or multiple peripheral lymphnode enlargements and diagnosed cytologically as TB lymphadenitis were included in the study. Aspirated samples were expressed on two glass slides and one is stained with Wright's stain for cytology, while the other is stained using the Ziehl Neelsen method for AFB. Cytologic findings were categorized in to three groups as non-caseating granuloma, caseating granuloma and pyo-histiocytic inflammation.

RESULTS

Only 52 (21.9%) aspirated samples were found to be positive for AFB. The most interesting finding in this study is that among the 52 AFB positive cases, 47 (53.4%) were cytomorphologically of the pyo-histiocytic type.

CONCLUSION

Detection of AFB varies with the cytomorphology of inflammation, being very high in pyo-histiocytic type.