Purpose: Tuberculous lymphadenitis is one of the most common presentations of extrapulmonary tuberculosis. The diagnosis can be challenging due to its varying clinical manifestations and the low sensitivity of conventional bacteriological methods for confirming the causative agent, Mycobacterium tuberculosis. Early secretory antigenic target 6 (ESAT-6), which is released early during M. tuberculosis infection and plays a role in granuloma formation, determines the pathogen’s invasion, its severity, and virulence factors related to the immune response. This study aimed to analyze the potential diagnostic value of ESAT-6 using real-time polymerase chain reaction (RT-PCR) and compare it with histopathologic diagnostics.

Materials and methods: This retrospective observational study with the cross-sectional design was conducted using consecutive sampling. A total of 50 formalin-fixed, paraffin-embedded lymph node tissue samples from lymphadenectomy consisted of 25 tuberculous lymphadenitis and 25 granulomatous lymphadenitis were collected. The specimens were diagnosed with tuberculous and granulomatous lymphadenitis based on histopathologic features. Analyses using conventional PCR from commercial kit to detect TB and RT-PCR to determine the expression of ESAT-6 were performed. Statistical analysis of the categorical data was performed using the Mann-Whitney test. Statistical significance was set at p < 0.05.

Results: The mean age of the patients was 35.66 years old (range: 6–85 years). The age group between 16 and 30 years was the most common (40%). Almost two-thirds (62%) of the patients were female. Sixteen (64%) tuberculous lymphadenitis and 13 (52%) granulomatous lymphadenitis samples were positive by PCR TB. ESAT-6 expression was significantly higher in tuberculous lymphadenitis (p = 0.004).

Conclusion: ESAT-6 as a potential predictor of tuberculous lymphadenitis can be used in patients for whom histopathologic diagnostics fail to confirm the presence of M. tuberculosis.

Global Tuberculosis Report 2019. Geneva: World Health Organization; 2019. Licence: CC BY-NC-SA 3.0 IGO

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