WIDE DIVERSITY IN MEASUREMENTS OF GROWTH-HORMONE AFTER STIMULATION TESTS IN SHORT CHILDREN ARE DUE TO ASSAY VARIABILITY

A comparison of three commercially available assays for growth hormone (Pharmacia hGH RIA, IDS Gamma-BCT GH and Delfia 22 kDa hGH) were used to measure growth hormone (GH) secretion in 26 short children after pharmacological stimulation. The IDS Gamma-BCT assay was compared with Pharmacia assay in 15 provocative tests (13 children; n = 94). The Pharmacia assay showed a strong positive proportional bias and this was particularly marked at GH > 20 mU/L; the mean difference between the assays at GH < 10 mU/L was 12%. The IDS Gamma-BCT assay was also compared with the Delfia 22 kDa assay in 18 provocative tests (13 children; n = 100). Results from the IDS assay was higher throughout the range 0-90 mU/L with a mean difference of 11.4% in the range 10-90 mU/L; the mean difference between the assays at GH < 10 mU/L was -39%.