Favorable prognostic significance of raised serum C3 concentration in patients with idiopathic focal glomerulosclerosis

This study examined the relationship between the clinical and pathologic variables and renal outcome in patients with idiopathic focal glomerulosclerosis (FGS). The study population included 106 patients with biopsy proven idiopathic FGS followed for a mean of 31 months. Forty-nine patients (46%) maintained stable renal function, 21 patients (20%) had a progressive deterioration of renal function and an additional 36 patients (34%) progressed to end-stage kidney disease. By multivariate analysis the following baseline variables (i.e. variables measured at the time of renal biopsy) were associated with the loss of renal function: 1. An elevated serum creatinine; 2. an elevated systemic blood pressure; 3. extensive interstitial fibrosis and tubular atrophy by kidney biopsy; 4. a low-normal serum C3 level. At baseline serum C3 levels were abnormally high in 31 patients (29%). Baseline C3 levels were inversely correlated with baseline serum creatinine levels (p<0.0001), the severity of histologic changes (p<0.0001), and better preservation of renal function during follow-up (p<0.0001). Serum C3 levels did not correlate with proteinuria or with other clinical variables tested. The presence of C1q in the mesangium did not correlate with renal outcome. In conclusion, serum C3 levels measured at the time of biopsy correlate with renal outcome in patients with idiopathic FGS. The basis for this correlation is unknown but it cannot be fully explained by relationships between serum C3 levels and other clinical variables.