Abstract: Objective: To evaluate the auxiliary value of interferon gamma-induced protein 10 (IP-10) mRNA release assay in the diagnosis for tuberculosis in different age groups. Methods: Totally 1590 suspected tuberculosis patients who were admitted to the Beijing Chest Hospital, Henan Infectious Diseases Hospital, and the Third People’s Hospital of Shenzhen from March 2018 to July 2022 and who finished IP-10 mRNA release assay before anti-tuberculosis therapy were prospectively recruited. A total of 1390 cases were included in the final analysis, and were divided into definite TB group (n=475), probable TB group (n=518) and non-TB group (n=397), according to the clinical diagnosis results. Other 200 cases with unclear diagnosis were excluded from the analysis. Furthermore, all the patients included in the analysis were further divided into two groups according to the age, the younger group (n=1062, 18-59 years) and the elderly group (n=328, 60-95 years). The diagnostic performance of IP-10 mRNA release assay were analyzed in the different age groups, based on the final diagnosis in clinic. Results: The sensitivity and specificity of IP-10 mRNA release assay were 90.2% (721/799, 95%CI: 87.9%-92.1%) and 68.8% (170/247, 95%CI: 62.6%-74.4%), respectively in the younger group, while 87.8% (159/181, 95%CI: 82.0%-92.0%) and 54.7% (76/139, 95%CI: 46.0%-63.1%), respectively in the elderly group. The specificity of IP-10 mRNA release assay in the younger group was significantly higher than that in the elderly group (χ²=7.704, P=0.006). However, there were no significant difference in the sensitivity between the two groups (χ²=0.922, P=0.337). There was no significant difference in the trend of diagnostic sensitivity of IP-10 mRNA release assay with the increasing age (Z=-1.063, P=0.288), but the diagnostic specificity was decreased significantly with the increasing age (Z=-2.846, P=0.004). Conclusion: IP-10 mRNA release assay is a promising test for auxiliary diagnosis of tuberculosis in younger patients; while considering the less impact of age on diagnostic sensitivity of IP-10 mRNA release assay, it may be helpful to use this technique for screening Mycobacterium tuberculosis infection in the elderly population.

Key words: Tuberculosis, Diagnosis, differential, Interferons, Interferon inducers