Comparison between the diagnostic validities of Xpert MTB/RIF and interferon-γ release assays for tuberculous pericarditis using pericardial tissue

BACKGROUND This study aimed to assess the diagnostic performance of Xpert MTB/RIF for tuberculous pericarditis (TBP) using pericardial tissues. METHODS The study involved 30 patients admitted with suspected TBP from January-December 2016; three patients were later excluded. The interferon-γ release assay (T-SPOT.TB) and the Xpert MTB/RIF test were performed using peripheral blood and pericardial tissues, respectively. TBP was confirmed using pericardial histopathology and a composite reference standard (CRS). We analyzed the sensitivity, specificity, predictive value (PV), likelihood ratio (LR), and area under curve (AUC) of both assays. RESULTS Fourteen patients were confirmed as TBP, 10 as non-TBP, and 3 as probable TBP. The sensitivity, specificity, positive PV (PPV), negative PV (NPV), PLR, NLR, and AUC (95% confidence interval [CI]) of the Xpert MTB/RIF assay were 78.6% (49.2-95.3%) and 70.6% (44.0-89.7%); 92.3% (64.0-99.8%) and 100% (69.2-100%); 91.7% (61.5-99.8%) and 100% (73.5-100%); 80.0% (51.9-95.7%) and 66.7% (38.4-88.2%); 10.21 (1.52-68.49) and the PLR value was undefined with CRS as the reference; 0.23 (0.08-0.64) and 0.29(0.14-0.61); and 0.854 (0.666-0.959) and 0.853 (0.664-0.959), against histopathology and CRS, respectively. The sensitivity, specificity, PPV, NPV, PLR, NLR, and AUC values (95% CI) of T-SPOT.TB were 92.9% (66.1-99.8%) and 94.1% (71.3-99.9%); 15.4% (1.9-45.5%) and 20.0% (2.5-55.6%); 54.2% (32.8-74.5%) and 66.7% (44.7-84.4%); 66.7% (9.4-99.2%) and 66.7% (9.4-99.2%); 1.10 (0.83-1.44) and 1.18 (0.84-1.6); 0.46 (0.05-4.53) and 0.29 (0.03-2.85); and 0.541(0.340-0.733) and 0.571(0.367-0.758), against histopathology and CRS, respectively. The differences in sensitivity, PPV, and AUC of Xpert MTB/RIF and T-SPOT.TB were not statistically significant (P > 0.05), compared to those of histopathology and CRS. However, the differences in specificity and NPV of the two assays were significant (P < 0.05), compared to those of histopathology and CRS. CONCLUSIONS Xpert MTB/RIF test is a valid diagnostic technique for TBP with higher sensitivity and specificity than T-SPOT.TB.