Whole-blood interferon-gamma release assay for diagnosis of tuberculous lymphadenitis

Tuberculosis remains a major problem for much of the world. Tuberculous lymphadenitis is the most common type of extrapulmonary tuberculosis, although a difficult invasive procedure is required for its diagnosis. We evaluated the usefulness of the whole-blood interferon-gamma release assay (IGRA) for diagnosis of tuberculous lymphadenitis. From January 2008 to October 2010, 108 patients underwent lymph node biopsy and the IGRA concurrently in Wonju Christian Hospital, Yonsei University Wonju College of Medicine. Among the patients, 27 were diagnosed with tuberculous lymphadenitis and 81 were diagnosed with non-tuberculous lymphadenitis. The diagnostic performances of the IGRA were evaluated. The median patient age was 33 years (interquartile range [IQR] 23.5 to 48 years), and 28 (25.9%) patients were male. No patient was administered immunosuppressive agents such as high-dose steroids or underwent chemotherapy within 90 days before the IGRA test. The IGRA was positive in 25 of 27 patients with tuberculous lymphadenitis and in 13 of 81 patients with non-tuberculous lymphadenopathy. Therefore, the sensitivity of IGRA was 92.6% (95% CI, 82.0 to 100), and the specificity was 80.2% (95% CI, 71.4 to 89.1). In the patients with positive IGRA results, the INF-γ concentration was significantly higher in the patients with tuberculous lymphadenitis compared to that in the patients without tuberculous lymphadenitis (15.58 [IQR 6.87 to 45.10] IU/mL versus 0.97 [IQR 0.65 to 2.41] IU/mL, p < 0.001). In conclusion, the IGRA is helpful for the diagnosis of tuberculous lymphadenitis.