Insulin-like growth factor I in cats: validation of an enzyme-linked immunosorbent assay and determination of biologic variation
2015 (English)In: Veterinary clinical pathology, ISSN 0275-6382, E-ISSN 1939-165X, Vol. 44, no 4, 542-551 p.Article in journal (Refereed) PublishedText
Background: Insulin-like growth factor I (IGF-I) measurements are used in veterinary medicine for diagnosing growth hormone disorders. IGF-I assays are subject to interference by IGF-binding proteins (IGFBP) which may not be efficiently removed by standard extraction methods. Adding excess IGF-II during analysis may improve accuracy. Objectives: The purpose of the study was to validate a commercial human IGF-I ELISA which uses excess IGF-II for feline samples and to evaluate biologic variation. Methods: Precision was determined by calculating the coefficient of variation (CV). Accuracy was determined by recovery after removal of IGFBP, addition of IGF-I, and linear dilution after the addition of IGFBP. Biologic variation was determined by repeated sampling in 7 cats. Results: There was interference by IGFBP in the high measuring range, resulting in falsely low IGF-I concentrations. This was overcome by the addition of high concentrations of IGF-II. Untreated serum had a measured/expected ratio of 98-115% compared to serum where IGFBP had been removed. Recovery after the addition of IGF-I was 83-112%. Inter and intra-assay CVs ranged from 2.4% to 5.0% which is within the minimum acceptance criteria based on biologic variation. The reference interval of IGF-I was wide (90-1207 ng/mL) and there was a significant association between body weight and ln IGF-I (P < .000001). Conclusions: This human ELISA is suitable for feline samples, but interfering IGFBP can cause falsely low concentrations. It is recommended to dilute samples such that IGF-I is < 28 ng/mL on the standard curve to grant for sufficient IGF-II for binding of interferent IGFBP.
Place, publisher, year, edition, pages
WILEY-BLACKWELL , 2015. Vol. 44, no 4, 542-551 p.
Growth hormone disorders; insulin-like growth factor-binding proteins; size-exclusion chromatography
IdentifiersURN: urn:nbn:se:liu:diva-125173DOI: 10.1111/vcp.12289ISI: 000368418900012PubMedID: 26418310OAI: oai:DiVA.org:liu-125173DiVA: diva2:903368
Funding Agencies|Agria and Swedish Kennel Club Research Foundation; Michael Forsgren Foundation2016-02-152016-02-152016-02-15