Background: There is a global focus on illness diagnosis in smear-negative and latent tuberculosis infectious populations (SN-TB and LTBI). CD27 has been suggested to play a direct role in active TB. Little is known about smear-negative individuals. Here, we tried to investigate whether it has a role in smear-negative populations. The expression of CD27 and MTB-specific CD27 in CD4+ T cells ("CD27-CD4+" and "CD27-IFN-γ+CD4+") was evaluated in MTB-unexposed controls (HC), TB contacts (TB-C) and SN-TB individuals by flow cytometry. The sensitivity, specificity and AUC (area under curve) of "CD27-IFN-γ+CD4+" cells to distinguish SN-TBs from HCs and TB-Cs were determined by receiver operating characteristic (ROC) curve analysis. The clinical index was selected from the clinical laboratory and evaluated for correlation with "CD27-IFN-γ+CD4+" cells by Spearman statistical analysis.
Results: We observed that the percentages of "CD27-IFN-γ+CD4+" cells were significantly increased in the SN-TB group compared with the HC and TB-C groups (AUC was 0.88, sensitivity was 82.14%, specificity was 80.00%, and P < 0.0001). The percentage of "CD27-IFN-γ+CD4+" cells was negatively correlated with WBC (white blood cell count) (r = - 0.3019, P = 0.0182) and positively correlated with IgE (immunoglobulin E) (r = 0.2805, P = 0.0362). Furthermore, "CD27-IFN-γ+CD4+" cells were significantly decreased, especially in the > 50 years group, after clinical treatment.
Conclusion: The present results demonstrated that the percentage of "CD27-IFN-γ+CD4+" cells might be a conceivable molecular indicator in the diagnosis of SN-TB and was influenced by its outcome of therapy.
Keywords: CD27; Diagnosis; Smear-negative pulmonary tuberculosis; Therapy.