ABSTRACT
BACKGROUND: Extra-pulmonary tuberculosis often presents a diagnostic challenge because of its diverse clinical manifestations and low yield of acid fast bacilli in tissue sections. AIM: The aim of the present study is immuno-histochemical localization of tuberculous bacilli or their components that persist in the granulomas but have lost the property of staining with acid fast stains and to assess the advantage of immuno-staining over conventional Ziehl Neelsen staining. MATERIAL AND METHODS: Immuno-histochemical staining using species-specific monoclonal anti-body to 38 kDa protein of Mycobacterium tuberculosis complex and Ziehl-Neelsen staining for acid fast bacilli (AFB) was done on 69; 36 cases of confirmed extra-pulmonary tuberculosis and 33 non-tuberculous cases, in archival formalin fixed paraffin embedded tissue sections OBERVATIONS: AFB positivity was observed in only 36.1% of tuberculous granulomas while immuno-histochemical staining was positive in 100% of tuberculous granulomata with zero false positivity and negativity. CONCLUSIONS: The immuno-hiostochemical localization of tuberculous bacilli and their components in tissue sections may be an efficient diagnostic adjunct to conventional ZN staining for the diagnosis of granulomas of extra-pulmonary tuberculosis. The technique is simple, sensitive and specific. It can be standardized and performed by trained technicians in routine laboratory. This will also help in clinical decision-making and in reducing the usual practice of prescribing empirical anti-tubercular treatment based on clinical suspicion alone in the absence of demonstrable evidence of tuberculous infection.