Determining the normal range for IGF-I, IGFBP-3, and ALS: new reference data based on current internal standards.

Area of Science:

• Pediatric Endocrinology
• Biochemical Markers
• Growth Disorders

Background:

• Insulin-like growth factors (IGF-I) and IGFBP-3 are key for diagnosing pediatric growth disorders.
• The utility of acid-labile subunit (ALS) in screening for ALS gene mutations requires further investigation.

Purpose of the Study:

• To establish reliable reference data for IGF-I, IGFBP-3, and ALS measurements in children and adolescents.
• To assess the role of ALS as a screening parameter for ALS gene mutations.
• To compare newly derived standard deviation scores (SDS) with existing data.

Main Methods:

• Measurement of IGF-I, IGFBP-3, and ALS in 252 pediatric samples using ELISA.
• Generation of reference curves with GAMLSS models and calculation of SDS.
• Bootstrap analysis for percentile uncertainty and Bland-Altman plots for SDS comparison.

Main Results:

• New reference data for IGF-I, IGFBP-3, and ALS assays are presented, suitable for SDS calculation.
• Discrepancies were observed in SDS calculations between new and previous reference data, particularly at lower SDS values (-2).

Conclusions:

• The generated IGF-I reference values are robust for diagnosing growth hormone deficiency (GHD) in prepubertal children.
• The study underscores the necessity of using labor- and method-specific reference data for accurate SDS calculation in growth disorder diagnostics.