Abstract
Inter-assay variation of antibody based routine tests is hampering comparability of measurement results for growth hormone (GH) between different laboratories and decision making in clinical practice. Here it is demonstrated, that quantification of GH by isotope dilution mass spectrometry (IDMS) constitutes a way to precise and reliable results which can be referred to in evaluation of performance of commercial test kits. With the IDMS method developed, tryptic cleavage products YSFLQNPQTSLCFSESIPTPSNR (T6) and LEDGSPR (T12) of GH are quantified by LC/MS-MS using the isotopically labeled forms of the peptides as internal standards. The GH cleavage fragments are obtained by whole-serum tryptic proteolysis and then extracted from the resulting mixture by semi-preparative reversed phase liquid chromatography followed by strong cation-exchange chromatography. Method validation basing on recovery of recombinant 22 kDa GH spiked to blank serum in defined amounts covering the intended concentration range (3-30 µg/L) would yield mean recoveries of 101.6% (100.7%), standard deviations of 2.5% (2.4%) and combined uncertainties (u~c~) of 3.0% (2.5%) if quantifying T6 (T12) as GH derived fragments, while the LOQ were 1.7 µg/L (2.7 µg/L). Potential to acquisition of reference values is exemplified by application to serum materials used in a recent quality assessment exercise for routine laboratories.
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Arsene, C., Henrion, A., Diekmann, N. et al. Quantification of growth hormone in serum by isotope dilution mass spectrometry. Nat Prec (2009). https://doi.org/10.1038/npre.2009.4050.1
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DOI: https://doi.org/10.1038/npre.2009.4050.1