Diagnostic value of TSPOT.TB, AFB smear microscopy, Genechip, and their combined application in Tuberculosis: a retrospective study.

Abstract Background : The Interferon-gamma release assay (IGRA) and Genechip are new tuberculosis diagnostic methods, but there have been limited studies conducted on combined application in tuberculosis. Starting in January 2021, Tangdu Hospital of Air Force Medical University began routinely using IGRA and Genechip. Therefore, the purpose of this study was to evaluate the efficacy of IGRA and Genechip, explore the feasibility of combined diagnosis, and provide guidance for the detection and diagnosis of tuberculosis in non-specialized hospitals. Methods : A retrospective study was conducted on 286 patients hospitalized at Tangdu Hospital of Air Force Medical University from January 1, 2021, to April 1, 2023. The diagnostic tests included IGRA (TSPOT.TB), Genechip, and acid-fast bacilli (AFB) smear microscopy. Active TB cases were determined based on a composite reference standard (CRS). The three methods were then compared and evaluated. Results : In total,286 patients simultaneous testing using TSPOT.TB, Genechip, and AFB smear microscopy methods. Among them, 36% (105/286) were diagnosed with active tuberculosis. The average age of these patients was 58.7±16.8 years old, with 55.6% (159/286) being over 60 years old and 44.4% (127/286) being under 60 years old. Regarding patients aged over 60 years old, the sensitivity, specificity, and AUC values for detecting tuberculosis using TSPOT.TB, AFB smear microscopy, and Genechip were 46.5%, 82.1%, 0.644; 17.2%, 99%, 0.581; and 74.1%, 98%, 0.861, respectively. For patients under 60 years, the sensitivity, specificity, and AUC values for detecting tuberculosis using TSPOT.TB, AFB smear microscopy, and Genechip were 44.6%, 85.0%, 0.648; 10.6%, 100%, 0.553; and 72.3%, 97.5%, 0.849, respectively. The AFB smear microscopy + Genechip combination had the highest diagnostic performance for patients aged over 60 years old, with a sensitivity of 84.4%, specificity of 97.0%, and AUC of 0.908. For patients under 60 years old, the TSPOT.TB + AFB smear microscopy + Genechip combination had the highest diagnostic performance, with a sensitivity of 97.8%, specificity of 82.5%, and AUC of 0.902. Conclusions : Genechip showed both high sensitivity and specificity, suggesting its high value in the diagnosis of tuberculosis. However, the combination of TSPOT.TB, AFB smear microscopy, and Genechip had higher diagnostic efficacy and was more effective in diagnosing tuberculosis.