Human growth hormone measurement by means of a sensitive ELISA of whole blood spots on filter paper

Background: Measurements of human growth hormone (hGH) are a prerequisite for identifying a deficiency or excess. Our study is the first to investigate the reliability of a very sensitive assay for the quantification of GH in dried blood spots on filter paper. Objective: Validation of a commercially-available enzyme-linked immunoassay (ELISA) for measuring hGH from filter paper samples of dried blood. Methods: We used an assay system (ELISA, E022, Mediagnost) based on polyclonal rabbit antibodies. Its suitability is ascribable to its very high sensitivity (1.6 ng/L) and virtual absence of interfering factors, excepting for a cross-reactivity with high pegvisomant concentrations. Results: hGH was found to be stable in dried blood spots on filter paper (No. 903. Whatman) over eight days at 37 degrees C. Extraction of hGH from filter paper, in comparison to EDTA plasma, was 107% (SD 8.1%; n = 6) over a range from 2.4 to 34.5 mu g/L. Linear regression analysis (n = 119) showed a correlation of R-2 = 0.97 for the hGH concentration in serum and oil filter paper samples. Conclusion: Our findings demonstrate the reliability of measurements of hGH in dried blood spots on filter paper. The advantages of this method are the low sample volume and the easy transport, storage, and handling of samples. This method contributes to the standardisation of diagnostics pertaining to abnormal hGH secretion as it facilitates the comparison of decisive measurements. (C) 2008 Elsevier Ltd. All rights reserved.