Discriminatory performance of insulin-like growth factor 1 and insulin-like growth factor binding protein-3 levels by correlating values to chronological age, bone age, and pubertal status for the diagnosis of isolated growth hormone deficiency

Purpose The discriminatory performance of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) levels was investigated by correlating their values with chronological age (CA), bone age (BA), and pubertal status (PS) for the diagnosis of isolated growth hormone deficiency (IGHD). Methods We evaluated IGF-1 and IGFBP-3 levels in 310 short stature subjects subdivided into two groups: IGHD (n=31) and non-IGHD (n=279). IGF-1 and IGFBP-3 were assayed by using immune-radiometric assay and transformed into standard deviation scores (SDS) according to CA, BA, and PS. Results The highest sensitivity was found in IGF-1-SDS for CA and IGFBP-3-SDS for CA (22.6% and 30.0%, respectively). The highest specificity was found in IGF-1-SDS for PS and IGFBP-3-SDS for PS (98.2% and 94.4%, respectively). Groups with the highest positive predictive value were IGF-1-SDS for BA and IGFBP-3-SDS for BA (10.9% and 5.1%, respectively). Highest negative predictive value were seen in IGF-1-SDS for CA and IGFBP-3-SDS for CA (98.4% and 98.4%, respectively). Conclusions IGF-1-SDS for CA, instead of IGF-1-SDS for BA or PS, could be used as a standard variable for IGHD screening. The highest specificity of IGF-1-SDS for PS suggests that this value is also useful tool for predicting IGHD.