Monoclonal Anti 38-KD Immunohistochemistry: A Novel Method for Improving the Diagnosis of Pediatric Tuberculous Lymphadenitis

Background: The clinical and histological criteria used to diagnose lymphadenitis caused by MTB organisms have low sensitivity, and poor specificity. We report a novel method for diagnosis of pediatric tuberculosis that uses Monoclonal anti 38-KD immunohistochemistry (IHC) to detect the 38- KD antigen on formalin-fixed tissue biopsies. This antigen has not been detected in non- tuberculous mycobacteria. Polymerase chain reaction (PCR) for amplification of IS6110 from DNA obtained from the biopsies was used as a gold standard in this Study. Methodology: Of 718 lymphadenopathy cases, 42 pediatric cases of granulomatous lymphadenitis with histologically suspected tuberculosis obtained from Sudan were evaluated. Z. N stain, IHC and PCR techniques were used for diagnosis. Positive and negative control for IHC and PCR were used to standardize the assays. Result: Z. N stain, IHC, and PCR positivity were observed in 1/42 (2.4 %), 33/42 (78.6 %), and 33/42 (78.6 %) of granulomatous lymphadenitis cases respectively. Z. N stain had sensitivity, specificity, sensitivity, specificity, PPV and NPV of 2.9 %, 100 %, 100 %, and 55 % respectively, while IHC had sensitivity, specificity, PPV and NPV of 100 %, 100 %, 100 %, and 100 %, respectively. Conclusion: IHC with anti-38-KD antiserum is a rapid, sensitive, and specific method for establishing an etiological diagnosis of Pediatric tuberculosis in histologic specimens. It can be standardized and performed by trained technicians in routine laboratory.