IGF-I for the diagnosis of growth hormone deficiency in children and adolescents: a reappraisal

A number of studies have evaluated the role of IGF-I measurement in the diagnosis of growth hormone deficiency (GHD). This study aimed to evaluate the accuracy and the best cut-off of IGF-I SDS in the diagnosis of GHD in a large cohort of short children and adolescents. One-hundred and forty-two children and adolescents with GHD [(63 organic/genetic (OGHD), 79 idiopathic (IGHD)] and 658 short non-GHD children (median age 10.4 y) were included in the analysis. The two groups were subdivided according to age (G1 <6, G2 6<9, G3 9<12, G4 ≥12) and to pubertal status. Serum IGF-I was measured by the same chemiluminescence assay in all samples and expressed as age and sex-based SDS. Receiver operating characteristic (ROC) analysis was used to evaluate the optimal IGF-I SDS cut-off and the diagnostic accuracy. Median IGF-I SDS was significantly lower in the GHD than in non-GHD patients. The Area Under the Curve (AUC) was 0.69, with the best IGF-I cut-off of -1.5 SDS (sensitivity 67.61%, specificity 62.62%). The AUC was 0.75 for OGHD and 0.63 for IGHD. The accuracy was better in the pubertal (AUC=0.81) than the prepubertal group (AUC=0.64). In our cohort IGF-I measurement has poor accuracy in discriminating GHD from non-GHD. Our findings confirm and reinforce the belief that IGF-I values should not be used alone in the diagnosis of GHD but should be interpreted in combination with other clinical and biochemical parameters.