Abstract:

Objective: The specific ligand protein SMAD2 was used to detect multiple tuberculosis antigens in patients, we aim to explore its diagnostic value for active tuberculosis. Methods: 152 tuberculosis patients who were admitted to Beijing Chest Hospital affiliated to Capital Medical University from January to March, 2023 were selected for tuberculosis-related examinations such as sputum smear, sputum culture and fluorescence PCR, and 177 healthy people receiving health checkup at the same time were selected as research objects. Based on SMAD2 ligand protein’s characteristic of capturing multiple tuberculosis antigens, a specially designed enzyme-linked immunosorbent assay (ELISA) was used to detect the content of tuberculosis antigen (expressed by A₄₅₀) in the serum of tuberculosis patients and healthy controls, and receiver operating characteristic (ROC) curve was used to analyze its diagnostic value. Results: The content of tuberculosis antigen in tuberculosis patients and healthy controls were 0.589 (0.426,0.807) and 0.257 (0.209,0.340) respectively, and the difference was statistically significant (Z=13.050, P<0.001). The results of ROC curve analysis showed that the AUC of SMAD2-based detection method for distinguishing tuberculosis patients from healthy people was 0.917 (95%CI: 0.889-0.946), the diagnostic sensitivity under the maximum Yoden Index was 90.13% (95%CI:84.36%-93.93%), and the specificity was 78.53% (95%CI:71.91%-83.94%). The positive and negative predictive value were 78.29% (137/175) and 90.26% (139/154), respectively. The accuracy rate was 83.89% (276/329), the misdiagnosis rate was 21.47% (38/177), and the missed diagnosis rate was 9.87% (15/152). The positive detection rates of bacteriologically positive and negative patients were 90.37% (122/135) and 88.24% (15/17) respectively, with no statistical significance difference between them (χ²=0.077, P=0.781). The positive detection rates of PCR positive and negative patients were 88.18% (97/110) and 95.24% (40/42) respectively, with no statistical significance difference between them (χ²=1.702, P=0.192). Conclusion: The SMAD2-based detection method has potential value for auxiliary diagnosis of active tuberculosis, especially for bacteriologically negative tuberculosis.

Key words: Smad2 protein, Mycobacterium tuberculosis, Antigen, Diagnosis