2 The technologies
2.1 Procalcitonin is involved in maintaining calcium levels in the blood and is an indirect biomarker of infection. It is released into the circulation in response to pro‑inflammatory stimuli, especially those originating from bacteria. Procalcitonin testing can be used to help clinicians to diagnose bacterial infection (that can cause sepsis) and guide decisions on starting antibiotic treatment. Procalcitonin levels are usually low in people with viral infections, chronic inflammatory disorders or autoimmune processes.
2.2 Thermo Fisher Scientific has a patent for using procalcitonin as a biomarker for sepsis. However, other companies have also licensed the use of procalcitonin and its antibodies. All commercial quantitative BRAHMS PCT assays use the same 'sandwich ELISA' principle to quantify procalcitonin by forming antibody–procalcitonin–antibody complexes. The main difference between these assays is the mechanism of detection of these complexes.
2.3 Five procalcitonin assays were identified during scoping as relevant to this assessment: the BRAHMS PCT Sensitive Kryptor assay (Thermo Fisher Scientific), the VIDAS BRAHMS PCT assay (bioMerieux), the ADVIA Centaur BRAHMS PCT assay (Siemens Healthcare Diagnostics), the Elecsys BRAHMS PCT assay (Roche Diagnostics) and the LIAISON BRAHMS PCT assay (DiaSorin). These assays have all been standardised using the BRAHMS PCT LIA assay (the original manual procalcitonin assay that is not in widespread use in the UK).