Low serum complement 3 level is associated with severe ANCA-associated vasculitis at diagnosis

Hyeok Choi, Youhyun Kim, Seung Min Jung, Jason Jungsik Song, Yong Beom Park, Sang Won Lee

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Objectives: We investigated whether low serum C3 level can cross-sectionally estimate severe antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) in immunosuppressive drug-naïve patients at diagnosis. Methods: We retrospectively reviewed the medical records of 139 patients with AAV, who were first classified as AAV at Severance Hospital. We obtained clinical and laboratory data including serum complement 3 (C3) level and calculated Birmingham vasculitis activity score (BVAS) at diagnosis. We stratified AAV patients into three groups according to the tertile of BVAS and defined the lower limit of the highest tertile as the cutoff for severe AAV (BVAS at diagnosis ≥ 16) at diagnosis. Low serum C3 level was defined as C3 < 90 mg/dL. The odds ratio (OR) was assessed using the multivariable logistic regression. Results: The mean age at diagnosis was 56.3 years and 41 patients were men (29.5%). The mean initial BVAS was 12.8. The mean serum C3 and C4 levels were 110.6 and 26.8 mg/dL. Thirty-one patients (22.3%) exhibited low serum C3 level at diagnosis. In the multivariable analysis, serum C3 level at diagnosis < 90 mg/dL (OR 2.963) exhibited the significant association with severe AAV at diagnosis. Patients with low serum C3 level exhibited a significantly high relative risk (RR) for severe AAV at diagnosis compared to those without (RR 3.600). Patients with low serum C3 level at diagnosis exhibited poor renal prognosis than those without. Conclusion: Low serum C3 level can estimate severe AAV and predict poor renal outcome in immunosuppressive drug-naïve patients at diagnosis.

Original languageEnglish
Pages (from-to)223-230
Number of pages8
JournalClinical and Experimental Nephrology
Issue number2
Publication statusPublished - 2019 Feb 15


All Science Journal Classification (ASJC) codes

  • Physiology
  • Nephrology
  • Physiology (medical)

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