Quantitation of serum IgG by solid-phase radioimmunoassay.

Human serum immunoglobulins are most frequently measured by single gel diffusion. Radioimmunoassay by use of antibodies bonded to particles is faster and more sensitive, precise, accurate, and specific. We adopted a solid-phase radioimmunoassay (SPRIA) technique, developed in our laboratory, to measure serum. lgG, and compared the results with those of a gel-diffusion method commonly used to measure serum lgG. The SPRIA technique is based on competition set up between antibodies to human lgG chemically bonded to cellulose particles and a purified serum IgG labeled with 1251. The solid phase permits prompt separation of the bound from free labeled reagent. We studied precision, accuracy, sensitivity, and specificity, as compared to gel diffusion; values for the two methods agreed well for 57 sera from hospital patients. The SPRIA procedure is more precise, and can be completed in 3 h, as compared to the 16-24 h normally required for gel diffusion procedures. The possible automation of SPRIA is discussed.