Abstract: Objective Through the clinical application of γ interferon release Assay(IGRA) in primary outpatient tuberculosis screening, the application effect and influencing factors can be evaluated to provide reference opinions for correct and reasonable clinical use. Method 3073 suspected newly diagnosed pulmonary tuberculosis patients who were treated at the Longhua District Chronic Disease Prevention and Control Center in Shenzhen from January 2021 to December 2022 were selected, and sputum samples were collected using acid-fast stain（AFS), BACTEC-MGIT 960 liquid culture method, and other methods crossing-primer amplification (CPA) technology was used to detect Mycobacterium tuberculosis (MTB) in sputum samples before treatment. Peripheral blood samples were collected for IGRA, and positive MGIT 960 liquid culture was used as the reference standard for tuberculosis infection. Clinical diagnosis was used as the diagnostic criterion to evaluate the detection efficiency of IGRA and other methods for tuberculosis infection. Result There is a significant statistical difference in the positive detection rate of IGRA among patients of different ages, with the highest positive detection rate in the 30-40 year old group and the lowest in the 0-10 year old group, with males being higher than females (P<0.01). Among several methods, the overall diagnostic accuracy of culture and CPA were 77.62% and 66.88%, respectively, which were significantly better than IGRA. The sensitivity and specificity of IGRA were 72.89% and 40.96%, respectively, with an overall diagnostic accuracy of only 59.04%. IGRA combined with culture or CPA can significantly improve detection sensitivity (86.89% and 84.22%), but there is no significant improvement in overall diagnostic efficiency (67.39% vs 77.62%, 65.86% vs 66.88%). The clinical diagnostic accuracy of IGRA for confirmed tuberculosis patients was 72.89%, with a false negative rate of 27.11%. The clinical diagnostic accuracy with non tuberculosis patients was 40.96% (136/332), with a false positive rate of 59.34%. The positive and negative predictive values for tuberculosis diagnosis were significantly lower than those of culture. There was no significant difference in the detection rate of IGRA for bacterial negative tuberculosis and bacterial positive tuberculosis (χ²=0.147, P=0.7014). Conclusion Although IGRA has good sensitivity, there are certain false positive and false negative rates in practical applications. Compared to pathogen detection, it has advantages in early screening of target disease or close contacts. However, its effectiveness in eliminating tuberculosis is insufficient, and it can be combined with other methods to improve its detection efficiency.

Key words: Mycobacterium tuberculosis, Phlegm culture, Crossing-primer amplification, Interferon gamma release assay, Comparative analysis