A newly developed and now internationally recognised primary method of measurement enables PTB to offer the calibration of biomarker rapid tests as the first national metrology institute. The aim of this new method is to ensure the better reliability and comparability of clinical laboratory tests.
For the early diagnosis of life-threatening diseases, tests with so-called biomarkers play an increasingly large role. In this case, biomarkers are substances contained in the blood which, at certain concentrations, are typical of certain diseases. Rapid tests can detect such compounds relatively fast and with little effort. However, depending on the manufacturer and the laboratory, the results of such assays can differ considerably from one another. A comparison showed differences of more than one order of magnitude in the results of rapid tests. Such inaccuracies can lead to false diagnoses which are a psychological strain for the patient and can even be life-threatening; furthermore, they can lead to unnecessary costs for the health care system.
Therefore, together with doctors of the Medizinische Klinik – Innenstadt of the Ludwig-Maximilians-Universität in Munich, PTB has developed a novel method to measure proteins in blood serum. This method measures the human growth hormone – which also plays a role in doping. Its analytical reliability and accuracy are based on the application of isotope dilution mass spectrometry (IDMS). This principle has been applied for a long time for the determination of target values for the quality control of diagnostic markers such as cholesterol, glucose, creatinine or steroid hormones, all of which are rather "small" molecules. The recent development transfers the measurement principle (IDMS) from "small" organic molecules to "biological" macro-molecules such as proteins. Thereby, amino acid chains are broken into small fragments which are easier to handle for analytical purposes, but which are still long enough to be unmistakably recognisable as fragments of the precursor protein. Chemical analysis, thereby, uses techniques belonging to the field of proteome research, especially enzymatic proteolysis.
This method represents a step towards filling the gap existing due to the lack of DMS-based target values in quality assurance for routine measurements of diagnostic protein markers.
Arsene,C. G.; Henrion, A.; Diekmann, N.; Manolopoulou, J.; Bidlingmaier, M.:
Quantification of growth hormone in serum by isotope dilution mass spectrometry, Analytical Biochemistry 401(2010) 228-235. Als Vorabdruck (frei erhältlich): Nature Precedings (07.12.2009), 
http://hdl.handle.net/10101/npre.2009.4050.1