Setting: Tuberculous lymphadenitis is the most common form of lymphadenopathy; its main histopathological finding is granulomatous inflammation.
Objective: A reverse blot hybridisation assay, REBA Myco-ID®, was applied to formalin-fixed paraffin-embedded (FFPE) tissue showing granulomatous lymphadenitis to define the causative agents.
Design: A total of 119 granulomatous lymphadenitis cases observed between 2000 and 2010 were studied. All tissue samples were treated by haematoxylin and eosin and Ziehl-Neelsen stain. Mycobacterium tuberculosis and non-tuberculous mycobacteria (NTM) were identified using the REBA Myco-ID assay, and resistance to rifampicin (RMP) and isoniazid (INH) was determined using REBA MTB-MDR®.
Results: Of the 119 cases, 113 (95%) were positive with the REBA Myco-ID assay, while 20 (16.8%) were positive on acid-fast bacilli smear. Of the 113 positive REBA Myco-ID cases, 110 (92.43%) were identified as M. tuberculosis, 2 (1.7%) as NTM, and 1 (0.8%) as co-infection with M. tuberculosis and M. chelonae. Only 1 (0.9%) of the 110 M. tuberculosis cases was identified as RMP-resistant.
Conclusion: REBA Myco-ID is a highly sensitive and specific assay for detecting M. tuberculosis and NTM. M. tuberculosis is the main cause of granulomatous lymphadenitis.