Procalcitonin in bacteraemia

Procalcitonin (PCT) is a prohormone that is produced by almost all organs and macrophages:

• is the precursor to calcitonin. Its half-life is between 22 and 35 h, and its levels begin to rise 3–4 h after inflammatory stimulation and peak at around 24 h after infection
  
• in healthy conditions, PCT is undetectable, but it rises quickly in response to pro-inflammatory stimuli, including bacterial infections and other inflammatory signals
  
• a randomised controlled trial in primary care relating to the treatment of acute respiratory tract infection (1):
  • revealed that PCT-guided therapy markedly reduces antibiotic use for acute respiratory tract infections in primary care without compromising patient outcome
  • authors suggest that PCT-guided therapy could be achieved with 1 to 2 PCT measurements in patients for whom the physician intends to prescribe antibiotics
    
• evidence shows that PCT-guided care can reduce antibiotic use without increasing infection or harm in patients with acute pancreatitis (2)
  
• a systematic review and meta-analysis revealed pooled sensitivities and specificities for detecting sepsis using PCT were 0.78 (95% CI: 0.74–0.81) and 0.77 (95% CI: 0.71–0.82) (3)

Diagnostic biomarker indications:

• NICE recommend considering PCT testing alongside standard blood investigations (FBC, CRP, U&Es, LFTs, blood gas) specifically in adults at moderate or high risk of severe illness or death to assist clinical decision-making on antibiotic administration (4)

References:

1. Briel M et al. Procalcitonin-guided antibiotic use vs a standard approach for acute respiratory tract infections in primary care. Intern Med. 2008 Oct 13;168(18):2000-7; discussion 2007-8
2. Siriwardena A et al. A procalcitonin-based algorithm to guide antibiotic use in patients with acute pancreatitis (PROCAP): a single-centre, patient-blinded, randomised controlled trial . Lancet Gastroenterology & Hepatology 2022 DOI: https://doi.org/10.1016/S2468-1253(22)00212-6
3. Chairaj T et al. Diagnostic performance of procalcitonin and presepsin in sepsis: a systematic review and meta-analysis. BMC Emerg Med. 2025 Dec 4;26(1):9.
4. NICE. Suspected sepsis in people aged 16 or over: recognition, assessment and early management (NG253). Published Nov 2025, updated Sep 2026. https://www.nice.org.uk/guidance/ng253