Figure 1. Measurement of GH in the same two samples A and B by different laboratories (n=208). Reported concentrations vary by more than 100% ( 1 ). The same results split by manufacturer reveal systematic differences between the respective assay methods. Three of the automated assays are shown as an example ( 2 ). Results taken from the External Quality Assessment Scheme 4/2017 organized by Reference Institute for Bioanalytics (RfB, Bonn, Germany), one of the two German proficiency testing organizations. More results can be accessed at http://www.rfb.bio.
