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Medline ® Abstract for Reference 39

of 'Diagnosis of growth hormone deficiency in children'

Evaluation of Variables Influencing the Measurement of Insulin-like Growth Factor-1.
Bancos I, Algeciras-Schimnich A, Grebe SK, Donato LJ, Nippoldt TB, Erickson D
Endocr Pract. 2014;20(5):421.
Objective: Our aim was to identify the frequency and possible clinical and analytical factors leading to "falsely" elevated insulin-like growth factor-1 (IGF-1).Methods: We performed a retrospective review of patients with IGF-1 concentrations above the reference interval. They were selected from a database of patients who had consecutive IGF-1 measurements between the years 2007-2010.Results: Out of 2,747 unique patients, 117 (4%) were found to have IGF-1 concentrations above the reference interval that were considered false-positives following a review of the clinical data. There was no relationship between the percentage of increase in IGF-1 and age, sex, body mass index (BMI), comorbidities, medication use, gonadal status, baseline growth hormone (GH), or insulin-like growth factor binding protein-3 (IGFBP-3) concentrations. An abnormal IGF-1 concentration led to performance of an oral glucose tolerance test (OGTT) for GH suppression in 21 of 117 patients (18%) and repeat IGF-1 measurements in 52 patients (44%). In 34 of 52 patients (65%) with a median follow-up of 36 months, the subsequent IGF-1 concentration was within the reference interval.Conclusion: Discovery of "falsely" elevated IGF-1 concentrations may lead to unnecessary testing and physician visits. Although the cause of the "falsely" elevated IGF-1 concentrations during the study period remains to beelucidated, it appears they are caused by a combination of high biological variability and method-specific assay performance issues. Clinicians should consider retesting patients with potentially spurious IGF-1 elevations after some time interval before embarking on more extensive investigations.
Division of Endocrinology, Metabolism and Nutrition, Department of Medicine, Mayo Clinic, Rochester, Minnesota.