Early secretory antigenic target 6 and culture filtrate protein 10 as diagnostic indicators in IgA nephropathy associated with renal tuberculosis

Background: This study evaluated the diagnostic value of early secretory antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) in immunoglobulin A nephropathy (IgAN) associated with renal tuberculosis (RT).Methods: Between January 2013 and January 2016, 40 patients with IgAN (IgAN group), 32 patients with RT (RT group), and 52 patients with IgAN associated with RT (IgAN + RT group) were selected for this study. A Tuberculin skin test (TST) was conducted, and serum Mycobacterium tuberculosis (MTB) antibody levels were measured. Urine samples were collected to culture MTB. Immunohistochemistry and western blotting were used to determine the expression of ESAT-6 and CFP-10 in renal tissues. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic values of ESAT-6 and CFP-10 in IgAN associated with RT.Results: TST, serum MTB antibody, and urine MTB assessments were negative in the IgAN group. The positive rates of the TST and serum MTB antibody and urine MTB testing were higher in the RT group than in the IgAN + RT group. Among the three groups, expression levels of ESAT-6 and CFP-10 were found to be the highest in the IgAN + RT group and were found to be the lowest in the IgAN group. The ROC curves indicated that the area under curve (AUC) value of ESAT-6 protein for IgAN + RT diagnosis was 0.907 with a cut-off of 26.72 as the critical value. Detection by ESAT-6 protein levels achieved 75.0% sensitivity and 94.2% specificity. The AUC value of the CFP-10 protein for diagnosis of IgAN + RT was 0.800, with a cut-off of 25.665 as the critical value. Detection by the protein levels of CFP-10 showed 63.9% sensitivity and 84.6% specificity.Conclusions: Our study provides evidence for the potential of the proteins ESAT-6 and CFP-10 as candidate markers for the diagnosis of IgAN associated with RT.