Measurement of serum IgA and C3 may predict the diagnosis of patients withIgA nephropathy prior to renal biopsy

The levels of serum IgA and C3 in patients with IgA nephropathy were determ ined using international standard serum (IFCC/CRM470) in a multicenter tria l in japan. The ratio of serum IgA to C3 (serum IgA/C3 ratio) without any i nformation from renal biopsy was used for the diagnosis of IgA nephropathy. Three hundred and six patients with IgA nephropathy and other glomerular d iseases, and 418 healthy adults were examined. The new diagnostic standardi zed criterion in patients with IgA nephropathy, obtained by nephelometric i mmune assay based on the international reference preparation CRM470, was 31 5 mg/dl. The serum IgA/C3 ratio was a more useful marker for distinguishing IgA nephropathy from non-Iga nephropathy together with serum IgA levels. T his suggests that the measurement of serum IgA and C3 may predict the diagn osis of patients with IgA nephropathy prior to renal biopsy. (C) 2000 Wiley -Liss, Inc.