Classification of Patients With GH Disorders May Vary According to the IGF-I Assay.

Abstract

Context:

Insulinlike growth factor I (IGF-I) measurement is essential for the diagnosis and management of growth hormone (GH) disorders. However, patient classification may vary substantially according to the assay technique.

Objective:

We compared individual patient data and classifications obtained with six different IGF-I assay kits in a group of patients with various GH disorders.

Design:

In this cross-sectional study, we measured IGF-I with six immunoassays in 102 patients with active or treated acromegaly or GH deficiency. IGF-I normative data previously established for the same six assay kits were used to classify the patients (high, low, or normal IGF-I levels), using both raw data and standard deviation scores (SDSs). Pairwise concordance between assays was assessed with Bland-Altman plots and with the percentage of observed agreement and the weighted κ coefficient for categorized IGF-I SDS.

Results:

We observed marked variability both across each individual's IGF-I raw data and across IGF-I SDS values obtained with each of the six immunoassays. Pairwise concordance between assay values, as assessed with the weighted κ coefficient, ranged from 0.50 (moderate) to 0.81 (excellent).

Conclusion:

Even when using normative data obtained in the same large population of healthy subjects and when using calculated IGF-I SDSs, agreement among IGF-I assay methods is only moderate to good. Differences in assay performance must be taken into account when evaluating and monitoring patients with GH disorders. This argues for the use of the same IGF-I assay for a given patient throughout follow-up.

• Authors: Maria Mavromati, Emmanuelle Kuhn, Hélène Agostini, Sylvie Brailly-Tabard, Catherine Massart, Marie-Liesse Piketty, Armelle Arnoux, Jacques Young, Jean-Claude Souberbielle, Philippe Chanson
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 102 Issue 8 Pg. 2844-2852 (08 01 2017) ISSN: 1945-7197 [Electronic] United States
• PMID: 28505364 (Publication Type: Journal Article)
• Copyright: Copyright © 2017 Endocrine Society

Chemical References

• Dopamine Agonists
• Ergolines
• Human Growth Hormone
• Somatostatin
• Insulin-Like Growth Factor I
• Cabergoline
• pegvisomant

Topics

• Acromegaly (metabolism, therapy)
• Adenoma (metabolism, therapy)
• Adult
• Aged
• Cabergoline
• Cross-Sectional Studies
• Dopamine Agonists (therapeutic use)
• Drug Therapy, Combination
• Dwarfism, Pituitary (metabolism)
• Ergolines (therapeutic use)
• Female
• Growth Hormone-Secreting Pituitary Adenoma (metabolism, therapy)
• Human Growth Hormone (analogs & derivatives, therapeutic use)
• Humans
• Immunoassay (methods)
• Insulin-Like Growth Factor I (metabolism)
• Male
• Middle Aged
• Neurosurgical Procedures
• Somatostatin (analogs & derivatives)
• Young Adult