IMMUNOMETRIC ASSAYS OF INSULIN AND ITS PRECURSORS

Assays of insulin and its precursors are of little diagnostic use but are essential for the study of the pathophysiology of non-insulin-depe ndent diabetes mellitus (NIDDM). The first assay for insulin was devel oped in 1956; however, early techniques overestimated insulin levels i n diabetics due to crossreactivity with proinsulin and 32, 33 split pr oinsulin, The use of monoclonal antibodies in two-site immunoradiometr ic assays overcame this problem and demonstrated the presence of beta cell dysfunction in NIDDM subjects, Conversion of the two-site immunor adiometric assays to immunoenzymometric assays using enzyme amplificat ion systems improved the sensitivity of the assays and also made them more user-friendly, Time-resolved fluorimetry has also been successful ly applied to the measurement of insulin and related molecules, Improv ements still need to be made to these assays, especially regarding the specificity of 32, 33 split proinsulin measurement and the sensitivit y of the assay for 65, 66 split proinsulin.