Abstract/Summary

Current requirements of the EU in-vitro diagnostic directive (IVDD) has established the requirement for routine devices to provide results that are traceable to higher order reference standards, where available. Routine blood tests are an essential component of prognostic and diagnostic medicine; however, these often use arbitrary international units (IU) to facilitate comparability, which lack metrological traceability. Whilst a number of certified reference materials (CRMs) are available for small molecules, little has been done in developing SI-traceable biological reference materials. In this thesis, the first task is to develop an SI-traceable quantified B-type natriuretic peptide (BNP) standard by adapting the current isotope dilution mass spectrometry (IDMS) methods. The standard is used to develop a reference method for the SI-traceable quantification of BNP in plasma. The difficulties associated with the purity assessment of synthetic peptides, stabilisation of BNP in plasma, measurement of large intact peptides by mass spectrometry (MS) and multiplexing the method for monitoring for the presence of degradation products are addressed. Many circulating peptides such as BNP, are routinely measured and External Quality Assessment Schemes (EQAS) are already established. BNP is an essential biomarker for heart failure. The reference method was used to participate in EQAS to assess the capability of the method to supply reference values to EQAS samples. The ultimate goal of the reference method to develop a commutable certified reference material (CRM) to assist the standardization of BNP measurements and to ascertain the direct benefits of metrological traceability in clinical diagnostics and evidence based medicine.This project also aims to include the higher order reference method in the Joint Committee for Traceability in Laboratory medicine (JCTLM) database.