Serum 25-hydroxyvitamin D levels in patients with Granulomatosis with Polyangiitis: association with respiratory infection

Abstract

OBJECTIVES: To determine the possible association of serum 25-hydroxyvitamin D (25OHD) levels with disease activity and respiratory infection in granulomatosis with polyangiitis patients during two different periods: winter/spring and summer/autumn. METHODS: Thirty-two granulomatosis with polyangiitis patients were evaluated in the winter/spring, and the same patients (except 5) were evaluated in summer/autumn (n = 27). The 25OHD levels were measured by radioimmunoassay. Disease activity was assessed by the Birmingham Vasculitis Activity Score Modified for Wegener's Granulomatosis (BVAS/WG) and antineutrophil cytoplasmic antibody (ANCA) positivity. Respiratory infection was defined according the Centers for Disease Control and Prevention criteria. RESULTS: 25OHD levels were lower among patients in winter/spring than in summer/autumn (32.31 +/- 13.10 vs. 38.98 +/- 10.97 ng/mL, p= 0.04). Seven patients met the criteria for respiratory infection: 5 in winter/spring and 2 in summer/autumn. Patients with respiratory infection presented lower 25OHD levels than those without infection (25.15 +/- 11.70 vs. 36.73 +/- 12.08 ng/mL, p= 0.02). A higher frequency of low vitamin D levels (25OHD <20 ng/mL) was observed in patients with respiratory infection (37.5% vs. 7.8, p= 0.04). Serum 25OHD levels were comparable between patients with (BVAS/WGX1 plus positive ANCA) and without disease activity (BVAS/WG= 0 plus negative ANCA) (35.40 +/- 11.48 vs. 35.34 +/- 13.13 ng/mL, p = 0.98). CONCLUSIONS: Lower 25OHD levels were associated with respiratory infection but not disease activity in granulomatosis with polyangiitis patients. Our data suggest that hypovitaminosis D could be an important risk factor for respiratory infection in granulomatosis with polyangiitis patients.