Detection of Insulin-Like Growth Factor 1 Variants by Mass Spectrometry: Results from a Clinical Reference Laboratory

To the Editor: In 2011, Bystrom et al. developed a top-down liquid chromatography- high-resolution mass spectrometry (LC-HRMS)1 assay for insulin-like growth factor 1 (IGF-1) quantification (1). Because V44M and R36Qreduce IGF-1 binding affinity to its receptor by 86 and 3.9-fold, respectively (4), and the A38V variant is located between arginine 36 and valine 44, this variant might also interfere with binding to the IGF-1 receptor. LC-HRMS, liquid chromatography-high resolution mass spectrometry; IGF-1, insulin-like growth factor 1; SNP, single nucleotide polymorphism; WT, wild type.