title: Screening diabetic cats for hypersomatotropism: performance of an enzyme-linked immunosorbent assay for insulin-like growth factor 1.
abstract: Screening diabetic cats for feline hypersomatotropism (HS) is currently dependent on using a radioimmunoassay (RIA) for measurement of growth hormone or insulin-like growth factor 1 (IGF-1), both of which require radioactivity, are costly and have limited availability. Performance of an enzyme-linked immunosorbent assay (ELISA) using anti-human IGF-1 antibodies was assessed. Total IGF-1 was determined in diabetic cat samples across a wide range of IGF-concentrations using a previously validated RIA (serum: 92 cats; plasma: 31 cats). Repeat IGF-1 measurement was then performed using the ELISA-system. Mean IGF-1 recovery after serial dilution proved satisfactory with a correlation coefficient of 0.96 (serum) and 0.97 (plasma). Appropriate precision was established [intra-assay coefficient of variation (CV) 9.5 ± 2% (serum) and 13.6 ± 7% (plasma); inter-assay CV 11.4 ± 4% (serum) and 7.6 ± 6% (plasma)] and significant effect of hyperlipidaemia, haemoglobinaemia, bilirubinaemia and storage was excluded, with the exception of an increase in serum IGF-1 when left at room temperature for more than 24 h. ELISA concentrations correlated significantly with RIA concentrations (serum Pearson r(2): 0.75; plasma: 0.83, P <0.001). Receiver operating characteristics analysis showed an area under the curve of 0.99 (serum) and 0.96 (plasma), and indicated high diagnostic accuracy for categorising a diabetic cat correctly as suspicious for HS at a serum IGF-1 cut-off of 997 ng/ml (sensitivity, 100%; specificity, 88.1%). The current study is the first to validate an easy-to-use and economical IGF-1 ELISA for the screening for HS among diabetic cats, which is important given the suspected significant prevalence of HS-induced diabetes mellitus.
authors.affiliation: 1Department of Veterinary Clinical Sciences, 'Ion Ionescu de la Brad' University of Agricultural Sciences and Veterinary Medicine Iasi, Romania.
authors.forename: Madalina
authors.initials: M
authors.lastname: Rosca
authors.forename: Yaiza
authors.initials: Y
authors.lastname: Forcada
authors.forename: Gheorghe
authors.initials: G
authors.lastname: Solcan
authors.forename: David B
authors.initials: DB
authors.lastname: Church
authors.forename: Stijn J M
authors.initials: SJ
authors.lastname: Niessen
mesh_terms: D000818:Animals; D000906:Antibodies; D002371:Cat Diseases / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism; D002415:Cats; D003920:Diabetes Mellitus / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary*; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*
chemical_list: D000906:Antibodies; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone