Relationship between serum IgA/C3 ratio and progression of IgA nephropathy

Intern Med. 2004 Nov;43(11):1023-8. doi: 10.2169/internalmedicine.43.1023.


Objective: The serum IgA/C3 ratio might be considered to serve as a diagnostic marker for patients with IgA nephropathy (IgAN), but its value as a marker of the severity of histological lesions or prognosis is unknown.

Methods: We studied the serum IgA/C3 ratio, using standardized reference material, in 86 patients with IgAN and in 32 with non-IgAN. The patients with IgAN were divided according to the severity of histological lesions (mild IgAN, n=29 and severe IgAN, n=57) based on Japanese clinical guidelines.

Results: The serum IgA level was significantly higher, while its C3 level was lower in patients with severe IgAN compared to those with non-IgAN. However, these levels were not different between patients with mild IgAN and non-IgAN. In contrast, the serum IgA/C3 ratio obviously differed among the three groups (2.47+/-0.96 vs. 3.63+/-1.44 vs. 4.72+/-1.86; p<0.01, ANOVA). Kaplan-Meier analysis of the patients with IgAN classified according to the mean serum IgA/C3 ratio revealed that the group with high serum IgA/C3 (4.5 and above) had a significantly poorer renal outcome (p<0.05, log-rank test), since the cumulative renal survival rate at 5 years was 84.4% vs. 100%. The ratio (%) of patients with severe IgAN in whom hematuria disappeared, was significantly higher in the low, than in the high serum IgA/C3 group (41.9% vs. 15.4%; p<0.05, t-test).

Conclusion: The serum IgA/C3 ratio appears to reflect the histological severity of IgAN and could serve as a marker of the progression of IgAN.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Complement C3 / metabolism*
  • Disease Progression
  • Female
  • Glomerulonephritis, IGA / blood*
  • Glomerulonephritis, IGA / physiopathology
  • Humans
  • Immunoglobulin A / blood*
  • Kidney Function Tests
  • Kidney Glomerulus / pathology
  • Male
  • Prognosis
  • Survival Analysis


  • Complement C3
  • Immunoglobulin A