A radioreceptor assay for serum insulin.

A method is described for the measurement of insulin in serum by RRA with normal human sRRA. The sensitivity of the assay is similar to that of a commonly used immunoassay. There is no detectable interference from somatomedin or NSILA, whereas proinsulin has only about 5% of the activity of insulin in the assay. There is a high degree of correlation between the results of immunoassay and the RRA over the physiological range of serum insulin. However, the greater ability to differentiate between insulin and proinsulin, together with greater ability of receptor binding to exclude altered (biologically inactive) insulin, present advantages of this assay over the RIA, which may be significant in abnormal situations.