Abstract

Diagnosis of tuberculous lymphadenitis can be an enigma owing to its varied clinical manifestation and also due to the low sensitivity of conventional bacteriological methods to confirm the presence of Mycobacterium tuberculosis. The present study was precisely designed to evaluate the potential diagnostic application of immunohistochemistry using a panel of antibodies against mycobacterial antigens for the diagnosis of tuberculous lymphadenitis. Immunohistochemistry was performed on the formalin-fixed paraffin sections of lymph node biopsies using rabbit polyclonal antibodies against four recombinant mycobacterial proteins, that is, ESAT-6, HspX, Tb8.4 and PlcA. The results of immunohistochemistry were correlated with Zeihl-Neelsen staining method. Immunohistochemistry using anti-ESAT-6 antibody was found to be highly sensitive (88.6%). Anti-ESAT-6 and anti-PlcA antibodies were found to be highly specific. Results of the study suggest that immunohistochemistry using anti-ESAT-6 antibody has potential application for the diagnosis of tuberculous lymphadenitis, in patients in whom conventional diagnostic methods did not confirm the presence of acid-fast bacilli.

Key words: Immunohistochemistry, tuberculous lymphadenitis, recombinant mycobacterial antigens.

Abbreviation

Abbreviations: TBL, Tuberculous lymphadenitis; IHC, Immunohistochemistry; AFB, Acid-fast bacillus; ZN, Ziehl-Neelsen; ATT, Antituberculous chemotherapy; FNA, Fine needle aspiration; ESAT-6, Early secreted antigenic target 6-kDa protein; Hsp, Heat shock protein; Plc, Phospholipase C.