Discrepancy of serum IgA levels determined by single radial immunodiffusion and laser nephelometry in patients with IgA nephropathy.

The levels of IgA in sera were quantitated by single radial immunodiffusion (SRID) and laser nephelometer (LN) to evaluate a precise amount of serum IgA in patients with IgA nephropathy, other glomerular diseases and healthy adults. Thirty patients with IgA nephropathy, twenty patients with other glomerular diseases and eighteen healthy adults were examined. It was shown that the levels of IgA in sera measured by LN were significantly higher than those in sera measured by SRID in patients with IgA nephropathy associated with increased levels of serum IgA. This suggests that the levels of serum IgA measured by SRID in patients with IgA nephropathy were affected by the physicochemical characteristics of circulating IgA in patients with IgA nephropathy. It is postulated that an increase of serum IgA in patients with IgA nephropathy may be mainly due to an increase of polymers rather than a monomer of IgA.