Diagnostic Utility of Interferon-γ Release Assay in Tuberculous Lymphadenitis

BACKGROUND: The diagnostic values of interferon-gamma release assays (IGRA) in tuberculous lymphadenitis (TBL) vary a lot in different research. We conducted a retrospective study to evaluate the diagnostic performance of T-SPOT.TB for suspected tuberculous lymphadenitis (TBL) patients. METHODS: Suspected tuberculous lymphadenitis patients with both T-SPOT.TB on peripheral blood mononuclear cells (PBMCs) and lymph node biopsy pathology were retrospective enrolled in this study from Peking Union Medical College Hospital (PUMCH) between September 2010 and December 2014. T-SPOT.TB results were evaluated against patients’ final diagnosis of TBL which was made based on clinical manifestations, radiology, microbiological and histopathological evaluation, and response to anti-TB treatment. The sensitivity, specificity, predictive value, and likelihood ratio of T-SPOT.TB were analyzed. RESULTS: Among the 52 patients enrolled, 5 confirmed TBL, 18 probable TBL and 16 non-TB were diagnosed respectively. 3 patients lost of follow up and 10 patients with clinically indeterminate diagnosis were not included in the final analysis. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) of T-SPOT.TB on PBMCs for diagnosing TBL were 95.7% (76.0%–99.8%); 75.0% (47.4%–91.7%), 84.6% (64.3%–95.0%), 92.3% (62.1%–99.6%), 3.826 (1.630–8.980), 0.058 (0.008–0.411) for T-SPOT.TB, respectively. Frequencies of spot forming cells (SFCs) of T-SPOT.TB were [526 (151–1248)/10(6) PBMCs] in TBL patients compared with [96 (34–674)/10(6) PBMCs] in non-TB patients, and no statistical difference was attained (P = 0.150). The best T-SPOT. TB cutoff value for TBL is 32 SFCs/10(6) PBMCs according to ROC curve, with the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) being 91.3% (70.5%–98.5%), 81.3% (53.7%–95.0%), 87.5% (66.5%–96.7%), 86.7%(58.4%-97.7%), 4.870(1.742–13.609), 0.107(0.028–0.414) respectively. CONCLUSION: T- SPOT.TB on PBMCs might be a rapid and accurate diagnostic test for TBL, with a high sensitivity and negative predictive value. DISCLOSURES: All authors: No reported disclosures.