Estimation of the biological variation of IGF-I in multimorbid geriatric patients and its clinical implications.

Abstract

Purpose: IGF-I is a well-established biomarker for detecting abnormalities in the growth hormone axis and evaluating effectiveness of growth hormone (GH) treatment. Common age-related diseases, such as sarcopenia are associated with impairments in the GH axis, making targeted GH therapy a potential treatment option. Nonetheless, data on the biological variation of IGF-I in older patients are missing, potentially leading to inaccurate interpretation of IGF-I concentrations in the diagnostic and therapeutic process. Our study aims to address this gap.

Methods: We conducted a retrospective analysis of IGF-I concentrations measured in samples from the geriatric outpatient facility of the Ludwig-Maximilians-University Hospital, Munich and the respective patient data from the MUnich SArcopenia Registry (MUSAR). Using a mixed-effects model, we estimated the intraindividual biological coefficient of variation (CVi). We calculated the Reference Change Values (RCV) and the Index of Individuality (II).

Results: 246 serum samples from 89 patients (mean age 83 years, range 70-97) were analyzed. The CV_i ranged from 13.4 to 15.6%, with a mean of 14.7%. RCV was 30.7% for a decrease and 44.3% for an increase in IGF-I concentrations. The II was 0.44.

Conclusion: The CV_i of IGF-I in our cohort differs from that previously described in younger and healthier populations and is therefore crucial for identifying significant changes in this geriatric cohort. The high degree of individuality also supports the application of personalized reference intervals. Our study provides data on the biological variation of IGF-I concentrations in geriatric patients; the calculated RCVs have the potential to refine interpretation.