C-peptide-measurement: a simple method for the improvement of specificity.

Sera containing insulin antibodies and proinsulin give artifactual high readings in C-Peptide measurement. This problem can be circumvented by the removal of antibodies and proinsulin prior to C-Peptide assay. A method is described which enables the removal of antibodies and proinsulin from sera without affecting the C-Peptide determination. Furthermore, this method allows a semiquantitative estimation of proinsulin, provided there is enough cross reactivity of the C-Peptide antibody with proinsulin.