Endocrine Abstracts

Objective: The concentration of GH (hGH) is important in the attribution of hGH therapy, for which in The Netherlands a national committee is responsible. Without this authorization re-imbursement is impossible. Therapy is permitted if all hGH concentrations after two stimulation tests are below 20 mU/l and in some clinical conditions independent of hGH. However, different assays produce different results and nationwide hGH results varied with CV ~30%. Consequently, authorization for hGH therapy depends on the laboratory that analyzes the samples, leading to social inequality. The national committee asked the Section of Endocrinology of the Dutch Foundation for Quality Assessment in Medical Laboratories to diminish nationwide variation.

Method: Since, standardization of assays is impossible, it was decided to harmonize hGH assays. A commutable sample was developed, being defined as behaving in all assays exactly as patients samples would do. The sample was obtained by mixing sera from healthy volunteers after 20 min of intensive exercise. Such samples contain all relevant isoforms due to de-novo synthesis of hGH. This sample was diluted with serum with low hGH concentration to obtain concentrations around the clinical decision limit of 20 mU/l. Next, it was freeze-dried and distributed to all participating laboratories. This harmonization sample was used to recalculate all hGH concentrations with a harmonization factor being the ratio of the measured and attributed concentration. In external quality control assessment schemes the reduction of variation was verified.

Results: After the introduction of the harmonization sample the nationwide variation of hGH assays dropped to <10%. Consequently, it was decided that laboratories must use the harmonizing method to assure that patients eligible for hGH therapy receive authorization with respect to social equality.

Conclusion: Harmonization of hGH assays is a valid method to reduce variation and to promote equality between patients when prescribing hGH therapy.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.