Sensibility and Specificity of Growth Factors in GH Deficiency.

The diagnosis of childhood onset GH deficiency (GHD) is often problematic especially for idiopathic, isolated GHD. No single physiologic or provocative test or combination of tests has proven to have sufficient specificity for the diagnosis of GHD. Due to their GH dependency and relative stability in the circulation, IGF-I and IGFBP-3 serum concentrations were proposed as reliable markers of daily GH secretion. Although specificity of the assays is high, multiple factors affect the measurements, reducing the sensitivity. In our experience, IGF-I sensitivity ranges from 70 to 75%, with a specificity ranging from 80 to 90%. IGFBP-3 assessment has low sensitivity, approximately 30%, and high specificity, approximately 100%. In conclusion, the sensitivity of assays for IGF-I and IGFBP-3 is too low to exclude the diagnosis of GHD on the basis of a normal value of the parameters. On the other hand, due to the high specificity, subnormal concentrations of IGF-I and/or IGFBP-3 strongly support the diagnosis of GHD. Finally, combining the assessment of height velocity with IGF-I measurement, sensitivity and specificity achieve a value equal to or above 95%.