Fluctuation of serum C3 levels reflects disease activity and metabolic background in patients with IgA nephropathy

Background: We focused on the fluctuations of serum C3 levels throughout the clinical course of patients and investigated the relationship between these fluctuations and clinical findings. Methods: IgA nephropathy patients (n = 122) were enrolled in the present study. Serum C3 and other clinical markers were compared at the time of renal biopsy and at last follow-up (6.67 +/- 2.07 years). Patients were divided into 3 groups based on serum C3 levels: Group I with first C3 levels below the mean -1 SD, which turned into an increase at last observation; group II with first C3 levels more than the mean +1 SD, which turned into a decrease at last observation; and group III, with first C3 levels more than the mean +1 SD, which turned into an increase at last observation. First and last levels of clinical markers were compared among the 3 groups. Results: Serum C3 levels of the patients whose renal symptoms, including hematuria, proteinuria and estimated glomerular filtration rate (eGFR), were improved, were significantly increased at last observation (p<0.05, p<0.01, p<0.01, respectively). Age, total cholesterol and triglyceride levels in group III were significantly higher than those in group I. Group II showed a significant reduction of urinary protein. Groups I and II maintained renal function, but group III showed a significant deterioration of renal function. Conclusions: The levels and fluctuations of serum C3 might reflect the disease activity and metabolic alteration in patients with IgA nephropathy.