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Research article - Peer-reviewed, 2012

Evaluation of an equine-optimized enzyme-linked immunosorbent assay for serum insulin measurement and stability study of equine serum insulin

Öberg, Josefine; Bröjer, Johan; Wattle, Ove; Lilliehöök, Inger

Abstract

This study aims to evaluate a commercially available equine-optimized insulin assay and to evaluate the stability of equine insulin. In addition, serum insulin concentrations before and after feeding are also presented. Samples were taken before and after feeding from 40 healthy horses and from 15 equine patients visiting the University Equine Hospital. Insulin was analysed with the equine ELISA and with two human methods (one ELISA and one RIA). Precision was determined by repeated analysis of samples on one assay run and from one sample analysed on 15 different assays. Recovery from two dilution series and from an additional study was evaluated. Stability of equine insulin was evaluated in samples with and without haemolysis stored at 18–20°C, 6–8°C for 30 days and at −20°C for 1 year. The equine assay correlated well with both human assays (r 2 = 0.97 for both assays). The intra-assay coefficient of variance (CV) was 2.0–6.5%, and the inter-assay CV was 10.7%. Recovery upon dilution was 82–100%, and recovery upon addition was 102–115%. There was no significant decrease in insulin concentrations for non-haemolyzed samples when stored at 6–8°C for 30 days or at −20°C for 1 year. Mean insulin concentration was significantly higher (347 ng/L) after feeding compared with before feeding (123 ng/L). The equine assay correlated well with the previously used assays. The assay had good precision and recovery after dilution and addition. A significant increase in mean insulin concentration was seen in horses after feeding

Keywords

Metabolic syndrome – Insulin resistance – Validation – ELISA – Horses – Diabetes mellitus

Published in

Comparative Clinical Pathology
2012, Volume: 21, number: 6, pages: 1291-1300