Evaluation of loop mediated isothermal amplification (LAMP) assay in the diagnosis of tubercular lymphadenitis: A pilot study

Tubercular lymphadenitis (TBLA) contributes to 30-40% of extrapulmonary TB cases in the immunocompetent individuals and 40-50% in people with HIV. Current diagnostic methods for TBLA like Gene-Xpert or PCR are costly and conventional methods like fine needle aspiration cytology, histopathology lack sensitivity and specificity. Culture which is considered as gold standard require high turnaround time. Loop mediated isothermal amplification (LAMP) assay has been developed as a novel technique for nucleic acid amplification and has shown promising results in the diagnosis of pulmonary tuberculosis. Present study evaluated the Nu-LAMPTM TB Kit (RAS Life Sciences Pvt. Ltd, a bioMerieux group company) for diagnosis of TBLA comparing with conventional tests (cytology, ZN smear, culture). The sensitivity, specificity, PPV and NPV of LAMP assay was found to be 33.3%, 91.2%, 40% and 88.57% as compared to 100%, 76.5%, 42.9% and 100% of ZN staining and 100%, 73.5%, 40% and 100% of cytopathology. The low sensitivity of LAMP assay in the present study addresses the need for comparison and validation of the commercially available LAMP kits before used for patient diagnosis.