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Development and Validation of an Ultrasensitive Single Molecule Array Digital Enzyme-linked Immunosorbent Assay for Human Interferon-α
Published on: June 14, 2018
Reference Values for IGF-I Serum Concentrations: Comparison of Six Immunoassays
Philippe Chanson1, Armelle Arnoux1, Maria Mavromati1
1Service d'Endocrinologie et des Maladies de la Reproduction and Centre de Référence des Maladies Endocriniennes Rares de la Croissance (P.C., M.M., J.Y.), Unité de Recherche Clinique (A.A.), and Service de Génétique Moléculaire, Pharmacogénétique et Hormonologie (S.B.T.), Assistance Publique-Hôpitaux de Paris, Hôpitaux Universitaires Paris-Sud, Hôpital de Bicêtre, Le Kremlin-Bicêtre, F94275, France; Inserm 1185 (P.C., S.B.T., J.Y.), Fac Med Paris Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, F-94276, France; and Laboratoire d'Hormonologie (C.M.), Centre Hospitalier Universitaire de Rennes, Centre d'Investigation Clinique Plurithématique, Inserm 1414, Hôpital Pontchaillou, Rennes, F29000, France; Service des Explorations Fonctionnelles (M-L.P., J.-C.S.), Assistance Publique-Hôpitaux de Paris, Hôpital Necker-Enfants Malades, Paris, F75015, France.
Context:
Measurement of IGF-I is essential for diagnosis and management of patients with disorders affecting the somatotropic axis. However, even when IGF-I kit manufacturers follow recent consensus guidelines, different kits can give very different results for a given sample.
Objectives:
We sought to establish normative data for six IGF-I assay kits based on a large random sample of the French general adult population.
Subjects And Methods:
In a cross-sectional multicenter cohort study, we measured IGF-I in 911 healthy adults (18-90 years) with six immunoassays (iSYS, LIAISON XL, IMMULITE, IGFI RIACT, Mediagnost ELISA, and Mediagnost RIA). Pairwise concordance between assays was assessed with Bland-Altman plots for both IGF-1 raw data and standard deviation scores (SDS), as well as with the percentage of observed agreement and the weighted Kappa coefficient for categorized IGF-I SDS.
Results:
Normative data included the range of values (2.5-97.5 percentiles) given by the six IGF-I assays according to age group and sex. A formula for SDS calculation is provided. Although the lower limits of the reference intervals of the six assays were similar, the upper limits varied markedly. Pairwise concordances were moderate to good (0.38-0.70).
Conclusion:
Despite being obtained in the same healthy population, the reference intervals of the six commercial IGF-1 assay kits showed noteworthy differences. Agreement between methods was moderate to good.
