Serum Procalcitonin Levels in Patients With Myeloperoxidase-Antineutrophil Cytoplasmic Antibodies-Associated Glomerulonephritis

Introduction: High serum procalcitonin (PCT) levels (>= 0.5 ng/mL) commonly occur with systemic bacterial and fungal infections. Although several studies suggested that measuring serum PCT levels may serve as a useful marker to distinguish between active antineutrophil cytoplasmic antibodies (ANCA)-associated diseases and invasive infections, there is no information on PCT in myeloperoxidase (MPO)-ANCA-associated glomerulonephritis. Methods: The authors measured serum PCT concentrations before initiation of immunosuppressive therapy in 67 patients with biopsy-proven MPO-ANCA-associated glomerulonephritis. The authors compared complications and clinicopathological parameters between patients with serum PCT levels of <0.5 ng/mL (group A: 58 patients) and >= 0.5 ng/mL (group B: 9 patients). Results: All 58 patients in group A did not show any clinical sign of systemic infection. On the other hand, 3 of 9 patients in group B had bacterial or fungal infections of the respiratory or urinary tact. One patient had a history of chronic urinary tract infection. In the remaining 5 patients in group B, there were 3 patients with concurrent malignancies and 1 postoperative patient with malignancy. Another in group B had a long history of interstitial pneumonia of unknown origin and severe renal insufficiency. Serum levels of C-reactive protein and creatinine were significantly higher in group B than in group A. Conclusions: In patients with MPO-ANCA-associated glomerulonephritis, serum PCT levels of >= 0.5 ng/mL are recommended as cutoff for consideration of bacterial and fungal infections. Elevated serum PCT levels could also be observed in some patients with severe injury of the kidneys and/or lungs in the absence of infection.