Value of renal biopsy in patients with renal dysfunction and ANCA positivity with anti-MPO and anti-PR3 specificity.

INTRODUCTION

ANCA-associated vasculitides with anti-MPO or anti-PR3 specificity cause inflammation of the glomerular capillary, leading to deterioration of renal function and potentially resulting in advanced kidney disease. Histological findings are overlapping for both subtypes; however, the genetic background differs, which may lead to differences in disease progression or response to treatment.

OBJECTIVES

To evaluate the differences between both subtypes in the progression of renal function and in the responses to treatments administered in real-world clinical practice at a single center.

MATERIALS AND

METHODS

Patients with impaired renal function and ANCA positivity with anti-MPO or anti-PR3 specificity who had undergone a renal biopsy were included.

RESULTS

A total of 113 patients were included, of whom 36% had histological findings different from those expected in the context of renal involvement due to vasculitis. No significant differences were found in the progression of renal function after treatment, nor between the different types of treatments administered. The determinants of renal survival were baseline creatinine levels, the presence of anti-GBM antibodies, and elevated levels of complement factor C4. A baseline creatinine level above 4mg/dL was associated with poorer renal survival.

CONCLUSIONS

In patients with impaired renal function and anti-MPO or PR3 ANCA specificity who undergo a renal biopsy, we do not find significant differences in the progression of renal function between ANCA vasculitis subtypes or according to the type of immunosuppressive treatment administered. A high percentage of patients present histological findings that differ from those expected.