Extensive study of human insulin immunoassays: promises and pitfalls for insulin analogue detection and quantification.

BACKGROUND: Over the last few decades, new synthetic insulin analogues have been developed. Their measurement is of prime importance in the investigation of hypoglycaemia, but their quantification is hampered by variable cross-reactivity with many insulin assays. For clinical analysis, it has now become essential to know the potential cross-reactivity of analogues of interest.
METHODS: In this work, we performed an extensive study of insulin analogue cross-reactivity using numerous human insulin immunoassays. We investigated the cross-reactivity of five analogues (lispro, aspart, glulisine, glargine, detemir) and two glargine metabolites (M1 and M2) with 16 commercial human insulin immunoassays as a function of concentration.
RESULTS: The cross-reactivity values for insulin analogues or glargine metabolites ranged from 0% to 264%. Four assays were more specific to human insulin, resulting in negligible cross-reactivity with the analogues. However, none of the 16 assays was completely free of cross-reactivity with analogues or metabolites. The results show that analogue cross-reactivity, which varies to a large degree, is far from negligible, and should not be overlooked in clinical investigations.
CONCLUSIONS: This study has established the cross-reactivity of five insulin analogues and two glargine metabolites using 16 immunoassays to facilitate the choice of the immunoassay(s) and to provide sensitive and specific analyses in clinical routine or investigation.