Abstract:

Objective: To evaluate the application value of QuantiFERON-TB Gold Plus (QFT-Plus) as a diagnostic adjunct for active pulmonary tuberculosis (PTB) and for monitoring anti-tuberculosis treatment response. Methods: A prospective study was conducted, patients with suspected PTB visiting the Outpatient Department of Integrated Traditional Chinese and Western Medicine Tuberculosis Division at Sixth People’s Hospital of Zhengzhou in Henan Province from June 2023 to April 2025 were screened based on the recruitment criteria. Recruited patients underwent basic demographic characteristic surveys, medical history assessments, and questionnaires on PTB-related suspected symptoms. Sputum and blood samples were collected for pathogen detection and QFT-Plus testing, respectively. According to the inclusion criteria, pathogen-positive drug sensitive PTB patients with excluded drug-resistant and non-tuberculous mycobacterial infections were classified as the “PTB group”, while pathogen-negative patients with excluded clinical diagnosis of PTB were categorized as the “other pulmonary diseases group”. The diagnostic performance of QFT-Plus for PTB was determined using the final clinical diagnosis as the reference standard. The QFT-Plus test results were monitored at baseline (T0), 4 weeks (T1), 8 weeks (T2), and 6 months (T3) of treatment, along with sputum culture outcomes. The correlation between the changes in the antigen tube of TB1, TB2 response and TB2-TB1, and the culture outcome were analyzed. Results: A total of 355 patients were recruited, of whom 134 patients were ultimately included in accordance with the inclusion criteria. Among them, 109 patients with PTB group, and 25 patients with other pulmonary diseases group. Referring to the final clinical diagnosis,the sensitivity, specificity, agreement rate, and Kappa value of QFT-Plus in detecting PTB were 88.07% (96/109), 76.00% (19/25), 85.82% (115/134), and 0.578, respectively. Among 35 PTB patients who completed monitoring at T1, T2, and T3, the QFT-Plus positive rates at the four time points were 97.14% (34/35), 88.57% (31/35), 82.86% (29/35), 77.14% (27/35), respectively, with no significant difference (Q_trend=7.415, P=0.060). The TB1 values at the four time points were 1.62 (0.96, 4.78), 1.48 (0.41, 3.57), 1.01 (0.31, 3.38), and 1.50 (0.45, 2.22) IU/ml, respectively. The corresponding values for TB2 were 2.97 (1.03, 5.79), 2.01 (0.65, 7.50), 1.27 (0.42, 4.02), and 1.92 (0.54, 2.96) IU/ml. Both indicators demonstrated a decreasing trend (Q_trend=9.221, P=0.027; Q_trend=10.730, P=0.013). However, the TB2-TB1 levels (0.12 (-0.03, 0.61), 0.05 (-0.07, 0.74), 0.01 (-0.08, 0.50), 0.07 (-0.02, 0.68) IU/ml) showed no significant differance (Q_trend=3.757, P=0.289). Conclusion: QFT-Plus testing can be used as an adjunctive tool for the diagnosis of PTB, but it is not yet supported as a reliable tool for monitoring treatment response.

Key words: Tuberculosis, pulmonary, Immunologic tests, Interferon-gamma, Diagnostic techniques and procedures, Treatment outcome, Monitoring, immunologic