title: Evaluation of immunoassays for the measurement of insulin and C-peptide as indirect biomarkers of insulin misuse in sport: values in selected population of athletes.
abstract: Insulin and C-peptide have been proposed as possible biomarkers of human insulin hormone misuse in sport. An extended intra- and inter-laboratory validation of commercially available immunoassays was performed. Enzyme Amplified Sensitivity Immunoassay (EASIA) assays (Human Insulin-EASIA and C-peptide EASIA kits from BioSource) were evaluated for insulin and C-peptide in serum. The intra- and inter-laboratory precision and accuracy values were good for the evaluated assays with maximum imprecision and inaccuracy of 16% and 23%, respectively, obtained just for one day C-peptide assay evaluation. The range of concentrations found in serum samples under investigation was always covered by the calibration curves of the studied immunoassays. However, a 19.7% of the samples felt below the estimated insulin limit of quantification. High concordance between laboratory results was obtained for insulin assay (intraclass correlation coefficient -ICC=0.857), whereas that for C-peptide was lower (ICC=0.539). Evaluated immunoassays were used to measure serum concentrations of insulin and C-peptide in elite athletes of various sport disciplines at different moment of training season, in recreational athletes at baseline conditions and finally in sedentary individuals. Serum insulin was statistically lower both in recreational and elite athletes when compared to sedentary individuals. Among elite athletes, the specific sport affected serum insulin (e.g., weightlifting) and C-peptide (e.g., triathlon) concentrations. Over the training season, a within athletes variability was observed for taekwondo, swimming and weightlifting athletes. Variations due to those aspects should be taken in careful consideration in the hypothesis of setting reference concentration ranges for doping detection.
authors.affiliation: Bioanalysis and Analytical Services Research Group, Neuropsychopharmacology Program, Institut Municipal d'Investigació Mèdica IMIM-Hospital del Mar, C/ Doctor Aiguader 88, 08003 Barcelona, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Abellan
authors.forename: Rosa
authors.initials: R
authors.lastname: Ventura
authors.forename: Ilaria
authors.initials: I
authors.lastname: Palmi
authors.forename: Simonetta
authors.initials: S
authors.lastname: di Carlo
authors.forename: Rita
authors.initials: R
authors.lastname: di Giovannandrea
authors.forename: Montse
authors.initials: M
authors.lastname: Bellver
authors.forename: Ramon
authors.initials: R
authors.lastname: Olive
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Pascual
authors.forename: Roberta
authors.initials: R
authors.lastname: Pacifici
authors.forename: Jordi
authors.initials: J
authors.lastname: Segura
authors.forename: Piergiorgio
authors.initials: P
authors.lastname: Zuccaro
authors.forename: Simona
authors.initials: S
authors.lastname: Pichini
mesh_terms: D000328:Adult; D015415:Biomarkers; D002096:C-Peptide / Q000097:blood*; D004300:Doping in Sports; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000097:blood* / Q000494:pharmacology*; D007118:Immunoassay; D007328:Insulin / Q000097:blood* / Q000494:pharmacology*; D008297:Male; D015233:Models, Statistical; D011786:Quality Control; D015203:Reproducibility of Results; D013048:Specimen Handling
chemical_list: D015415:Biomarkers; D002096:C-Peptide; D007004:Hypoglycemic Agents; D007328:Insulin