Analysis of the association between Mycobacterium tuberculosis infection and Immunoglobulin A nephropathy by early secreted antigenic target 6 detection in renal biopsies: a prospective study

ABSTRACT

Objectives: Immunoglobulin A nephropathy (IgAN) is the most frequent cause of primary renal disease, and clarifying the pathogenesis of IgAN is of great importance for its diagnosis and treatment. It is well known that Mycobacterium tuberculosis (MTB) can infect the urinary tract and result in the typical symptoms of cystitis. However, MTB can also affect the kidney more insidiously. Patients may present with glomerular disease, and sometimes with advanced renal failure. This study was to investigate the association between MTB infection and IgA nephropathy (IgAN), and the early diagnosis of MTB-mediated IgAN by means of early secreted antigenic target 6 (ESAT-6) detection in renal biopsies.

Methods: One hundred and twenty patients were divided into 3 groups: a renal tuberculosis (RTB) group, a glomerulonephritis without MTB infection (GN-TBI) group and a glomerulonephritis with MTB infection (GN+TBI) group. Morning urine samples were collected for MTB culture. Immunohistochemistry for ESAT-6 expression in renal tissues was performed.

Results: The incidence rate of IgAN in the GN+TBI group was 66.7%, which was significantly higher than that of the GN-TBI group. In the GN+TBI group, the ESAT-6 expression was positively associated with IgAN incidence. There was a statistical association between the positive expression of ESAT-6 and the incidence of IgAN. The sensitivity and specificity of urine MTB culture in diagnosing renal MTB infection was 23.3% and 100% respectively, while the sensitivity and specificity of ESAT-6 detection was 100% and 91.1% respectively. Compared with urine MTB culture, the sensitivity of ESAT-6 detection was significantly increased.

Conclusion: MTB infection might be associated with the occurrence of IgAN, and ESAT-6 detection in renal tissues may be helpful for the early diagnosis of MTB-mediated IgAN.

KEYWORDS:

• ESAT-6
• early diagnosis
• IgA nephropathy
• Mycobacterium tuberculosis

Acknowledgments

The authors would like to thank the staff of the Department of Nephrology in China Medical University for providing clinical assistance.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

This work was supported by the Foundation of Social Development Research Program of Liaoning Province (no. 2012225094) and the Program for Liaoning Excellent Talents in University (LJQ2013086).