The measurement of complement as an aid in diagnosis: 1. Nephritis and collagen disease.

A selection of patients with nephritis and collagen diseases were studied for complement abnormalities. This communication briefly reviews the current comcepts of complement physiology, details standard assay used in this laboratory and describes clinical examples where these tests have provided significant clinical information. Quantitative measurements of individual components, the presence of circulating immune complexes, and the demonstration of in vivo C3 cleavage products were assessed simultaneously. The importance of measuring cleavage products and immune complexes is stressed. Clinical examples are given where misleading or erroneous interpretation of results might have occurred if these tests had not been performed.