Procalcitonin (PCT) is a peptide precursor of the hormone calcitonin, the latter being involved with calcium homeostasis. It is composed of 116 amino acids and is produced by parafollicular cells (C cells) of the thyroid and by the neuroendocrine cells of the lung and the intestine.
The level of procalcitonin in the blood stream of healthy individuals is below the limit of detection (10 pg/mL) of clinical assays. The level of procalcitonin rises in a response to a proinflammatory stimulus, especially of bacterial origin. In this case, it is produced mainly by the cells of the lung and the intestine. It does not rise significantly with viral or non-infectious inflammations. With the derangements that a severe infection with an associated systemic response brings, the blood levels of procalcitonin may rise to 100 µg/L. In serum, procalcitonin has a half-life of 25 to 30 hours. Remarkably the high procalcitonin levels produced during infections are not followed by a parallel increase in calcitonin or a decrease in serum calcium levels.
Diagnosis and prognosis of sepsis
Measurement of procalcitonin can be used as a marker of severe sepsis caused by bacteria and generally grades well with the degree of sepsis, although levels of procalcitonin in the blood are very low. PCT has the greatest sensitivity (85%) and specificity (91%) for differentiating patients with systemic inflammatory response syndrome (SIRS) from those with sepsis, when compared with IL-2, IL-6, IL-8, CRP and TNF-alpha. Evidence is emerging that procalcitonin levels can reduce unnecessary antibiotic prescribing to people with lower respiratory tract infections. Currently, procalcitonin assays are widely used in the clinical environment.
Diagnosis of bacteremia
Prognosis of pneumonia
A cluster randomized trial found that the procalcitonin level can help guide antibiotic therapy. In this trial, "on the basis of serum procalcitonin concentrations, use of antibiotics was more or less discouraged (<0.1 μg/L or <0.25 μg/L) or encouraged (≥ 0.5 μg/L or ≥0.25 μg/L), respectively". However, an earlier nonrandomized, observational study reported "limited, prognostic value" of procalcitonin measurement. 1122
Procalcitonin levels may be useful to distinguish bacterial infections from nonbacterial infections. Trials from 2008 and 2009 have shown that they may help guide therapy and reduce antibiotic use, which can help save on cost of antibiotic prescriptions and drug resistance.
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- Meisner M, Tschaikowsky K, Palmaers T, Schmidt J (1999). "Comparison of procalcitonin (PCT) and C-reactive protein (CRP) plasma concentrations at different SOFA scores during the course of sepsis and MODS". Crit Care 3 (1): 45–50. doi:10.1186/cc306. PMC 29013. PMID 11056723.
- BalcI C, Sungurtekin H, Gürses E, Sungurtekin U, Kaptanoglu B (February 2003). "Usefulness of procalcitonin for diagnosis of sepsis in the intensive care unit". Crit Care 7 (1): 85–90. doi:10.1186/cc1843. PMC 154110. PMID 12617745.
- Schuetz P, Christ-Crain M, Thomann R, et al. (September 9, 2009). "Effect of procalcitonin-based guidelines vs standard guidelines on antibiotic use in lower respiratory tract infections: the ProHOSP randomized controlled trial.". JAMA 302 (10): 1059–1066. doi:10.1001/jama.2009.1297. PMID 19738090.
- Yealy DM, Fine MJ (September 9, 2009). "Measurement of serum procalcitonin: a step closer to tailored care for respiratory infections?". JAMA 302 (10): 1115–1116. doi:10.1001/jama.2009.1318. PMID 19738100.
- Jones AE, Fiechtl JF, Brown MD, Ballew JJ, Kline JA (2007). "Procalcitonin test in the diagnosis of bacteremia: a meta-analysis". Annals of Emergency Medicine 50 (1): 34–41. doi:10.1016/j.annemergmed.2006.10.020. PMID 17161501.
- Christ-Crain M, Jaccard-Stolz D, Bingisser R, Gencay MM, Huber PR, Tamm M, Müller B (2004). "Effect of procalcitonin-guided treatment on antibiotic use and outcome in lower respiratory tract infections: cluster-randomised, single-blinded intervention trial". Lancet 363 (9409): 600–7. doi:10.1016/S0140-6736(04)15591-8. PMID 14987884.
- Brunkhorst FM, Al-Nawas B, Krummenauer F, Forycki ZF, Shah PM (2002). "Procalcitonin, C-reactive protein and APACHE II score for risk evaluation in patients with severe pneumonia". Clin. Microbiol. Infect. 8 (2): 93–100. doi:10.1046/j.1469-0691.2002.00349.x. PMID 11952722.
- Schuetz P, Christ-Crain M, Thomann R, et al. Effect of procalcitonin-based guidelines vs standard guidelines on antibiotic use in lower respiratory tract infections: the ProHOSP randomized controlled trial. JAMA. Sep 9 2009;302(10):1059-66.
- Briel M, Schuetz P, Mueller B, et al. Procalcitonin-guided antibiotic use vs a standard approach for acute respiratory tract infections in primary care. Arch Intern Med. Oct 13 2008;168(18):2000-7; discussion 2007-8.
- Procalcitonin - web site of the manufacturer of the PCT assay.
- Procalcitonin at Lab Tests Online
- Procalcitonin: analyte monograph - The Association for Clinical Biochemistry and Laboratory Medicine