Improved diagnostic power by combined interferon-gamma release assay and nested-PCR in tuberculous pleurisy in high tuberculosis prevalence area.

The conventional acid fast bacilli (AFB) smear and Mycobacterium tuberculosis (M.tb) culture of pleural effusion and tuberculin skin test (TST) in tuberculous pleurisy are unable to meet clinical needs because of their low sensitivities and specificities. To evaluate the diagnostic accuracies of QuantiFERON TB Gold In-Tube test (QFT-GIT) and nested-PCR in tuberculous pleurisy, we conducted a cross-sectional study in regions of China with a high tuberculosis (TB) epidemic. Seventy-eight participants were enrolled: 58 TB patients with diagnosis of confirmed or probable tuberculous pleurisy and 20 non-TB patients with a diagnosis of other non-TB diseases. The positive rates of AFB smear and M.tb culture in the pleural effusion were 5.8% (2/42) and 10.6% (5/47), respectively. The sensitivity and specificity of QFT-GIT were 93.1% (54/58) and 90.0% (18/20), whereas those of TST were 68.5% (37/54) and 86.7% (13/15), respectively; the sensitivity of QFT-GIT was significantly higher than TST (P = 0.013). The sensitivity and specificity of M.tb-specific nested-PCR in pleural effusion were 94.8% (55/58) and 90.0% (18/20), respectively, with a turnaround time of 7 h. Furthermore, combined QFT-GIT and nested-PCR detection improves the specificity to 100% with a sensitivity of up to 90.0%. This combination of immunoassay and molecular detection holds promise for the clinical diagnosis of tuberculous pleurisy.