Development of a candidate reference method for the quantification of procalcitonin in human serum

Procalcitonin (PCT) measurement is a usefully tool to aid the early diagnosis and antibiotic stewardship for patients with sepsis. As sepsis diagnosis and antibiotic stewardship rely on fixed clinical cutoffs (threshold concentration values), ensuring accuracy and comparability of PCT results over time and space is essential to ensure an appropriate diagnostic and therapeutic management.

This thesis consisted in studying the metrological traceability of these methods of PCT measurement. The work initially consisted in documenting the current state for results’ comparability between the different commercially available immunoassays for PCT. The evaluation of correlation studies and external quality assessment schemes results indicate that properly evaluating the current state of result’s comparability and discriminating the origin of result’s discrepancies is made difficult because studies were conducted in non-harmonized conditions and commutability of the materials was not characterized. Thus, it seems essential to conduct quality external evaluation using commutable control materials. In order to evaluate accuracy of commercially available immunoassays for PCT and to meet the regulatory requirements for the metrological traceability of results, a candidate reference method based on isotopic dilution liquid chromatography coupled to mass spectrometry was developed and validated for an absolute quantification of PCT in human serum with a limit of quantification of 0.25 ng/mL. Results traceability to the SI units could be established thanks to a thorough purity assessment of the primary standards by amino acid analysis and correction of impurities contribution.

procalcitonin, sepsis, antibiotic resistance, isotope dilution liquid chromatography coupled mass spectrometry, reference method, metrological traceability