Insulin radioimmunoassay: inappropriately high results obtained using a preprecipitated antibody technique

A brief comparison of the results of three insulin radioimmunoassay methods indicated that insulin levels measured in heparinised plasma by a pre-precipitated antibody technique were inappropriately high. The error was greatest when low but clinically important levels of the hormone were studied. This effect was due to non-insulin components of the plasma and could be eliminated by the addition of insulin-free plasma to the standard tubes.