Comparative study of C reactive protein and serum amyloid A protein in experimental inflammation.

The responses of C reactive protein, measured by radial immunodiffusion and radioimmunoassay, and serum amyloid A protein, measured by radial immunodiffusion, were compared in eight subjects with inflammation induced experimentally by intradermal injection of monosodium urate crystals. A significant increase in serum amyloid A was noted after a lag phase of eight hours, the increase in median concentration at 48 hours being about eightfold. A parallel but less marked increase was found in C reactive protein when measured by radioimmunoassay (fourfold increase in median concentration at 48 hours) after a small but significant decrease during the lag phase. The changes in C reactive protein remained within the reference range and were not detectable by radial immunodiffusion.