Procalcitonin

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Procalcitonin (PCT) is a precursor of the hormone calcitonin, which is involved with calcium homeostasis, and is produced by the C-cells of the thyroid gland. It is there that procalcitonin is cleaved into calcitonin, katacalcin and a protein residue. It is not released into the blood stream of healthy individuals.

Measurement

With the derangements that a severe infection with an associated systemic response brings, the blood levels of procalcitonin may rise to 100 ng/ml. In blood serum, procalcitonin has a half-life of 25 to 30 hours.

There are two commercial kits for measuring the PCT.[1] The Kryptor assay has a lower limit of detection of 0.06 μg/L while the LUMI kit has a lower limit of detection of 0.3–0.5 μg/L. The Kryptor kit is thought by some to be better and more sensitive than the the LUMI test.[1] However, comparisons of their ability to prognosticate pneumomia as compared to using the c-reactive protein have conflicted with PCT by Kryptor being similar to[2] or better than[3] the c-reactive protein and PCT by LUMI being better[4]than the c-reactive protein.

Uses

Diagnosis and prognosis of sepsis

Measurement of procalcitonin can be used as a marker of severe sepsis and generally grades well with the degree of sepsis,[5] although levels of procalcitonin in the blood are very low. PCT has the greatest sensitivity (85%) and specificity (91%) for differentiating patients with SIRS from those with sepsis, when compared with IL-2, IL-6, IL-8, CRP and TNF-alpha.[6] However, the test is not routinely used and has yet to gain widespread acceptance.

In a comprehensive meta-analysis in 2007 the diagnostic accuracy of procalcitonin as a marker to differentiate sepsis from other non-infectious causes of systemic inflammatory responses was estimated including 18 studies (14 phase 2 and 4 phase 3 studies). [7] In this review the overall diagnostic performance of procalcitonin was low. The authors concluded that procalcitonin cannot reliably differentiate sepsis from other non-infectious causes of systemic inflammatory response syndrome in critically ill adult patients and should not be used as often as it is currently done in the critical care setting.

Diagnosis of bacteremia

A meta-analysis reported a sensitivity of 76% and specificity of 70% for the diagnosis of bacteremia.[8]

Prognosis of respiratory tract infection

A randomized controlled trial of patients with respiratory tract infections (more common diagnoses were rhinosinusitis and bronchitis), procalcitonin guided therapy reduces antibiotic use without compromising patient outcome.[9][10][11]

Prognosis of pneumonia

A cluster randomized controlled trial found that the procalcitonin level can help guide antibiotic therapy in patients with pneumonia. In this trial, "on the basis of serum procalcitonin concentrations, use of antibiotics was more or less discouraged (<0.1 microg/L or <0.25 microg/L) or encouraged (> or =0.5 microg/L or > or =0.25 microg/L), respectively".[12]. However, a nonrandomized, observational study reported "limited, prognostic value" of the procalcitonin[4].

References

  1. ↑ 1.0 1.1 Niederman MS (December 2008). "Biological markers to determine eligibility in trials for community-acquired pneumonia: a focus on procalcitonin". Clin. Infect. Dis. 47 Suppl 3: S127–32. DOI:10.1086/591393. PMID 18986278. Research Blogging.
  2. ↑ Holm A, Pedersen SS, Nexoe J, et al. (July 2007). "Procalcitonin versus C-reactive protein for predicting pneumonia in adults with lower respiratory tract infection in primary care". Br J Gen Pract 57 (540): 555–60. PMID 17727748. PMC 2099638. [e]
  3. ↑ Müller B, Harbarth S, Stolz D, et al. (2007). "Diagnostic and prognostic accuracy of clinical and laboratory parameters in community-acquired pneumonia". BMC Infect. Dis. 7: 10. DOI:10.1186/1471-2334-7-10. PMID 17335562. PMC 1821031. Research Blogging.
  4. ↑ 4.0 4.1 Brunkhorst FM, Al-Nawas B, Krummenauer F, Forycki ZF, Shah PM (February 2002). "Procalcitonin, C-reactive protein and APACHE II score for risk evaluation in patients with severe pneumonia". Clin. Microbiol. Infect. 8 (2): 93–100. PMID 11952722. [e] Cite error: Invalid <ref> tag; name "pmid11952722" defined multiple times with different content
  5. ↑ 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" 3 (1): 45-50. PMID 11056723. [e]
  6. ↑ BalcI C, Sungurtekin H, Gürses E, Sungurtekin U, Kaptanoglu B (2003). "Usefulness of procalcitonin for diagnosis of sepsis in the intensive care unit". Critical care (London, England) 7 (1): 85-90. PMID 12617745. [e]
  7. ↑ Tang BM, Eslick GD, Craig JC, McLean AS (2007). "Accuracy of procalcitonin for sepsis diagnosis in critically ill patients: systematic review and meta-analysis". The Lancet infectious diseases 7 (3): 210-7. DOI:10.1016/S1473-3099(07)70052-X. PMID 17317602. Research Blogging.
  8. ↑ 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. Research Blogging.
  9. ↑ Briel M, Schuetz P, Mueller B, et al (October 2008). "Procalcitonin-guided antibiotic use vs a standard approach for acute respiratory tract infections in primary care". Archives of internal medicine 168 (18): 2000–7; discussion 2007–8. DOI:10.1001/archinte.168.18.2000. PMID 18852401. Research Blogging.
  10. ↑ Christ-Crain M, Stolz D, Bingisser R, et al. (July 2006). "Procalcitonin guidance of antibiotic therapy in community-acquired pneumonia: a randomized trial". Am. J. Respir. Crit. Care Med. 174 (1): 84–93. DOI:10.1164/rccm.200512-1922OC. PMID 16603606. Research Blogging.
  11. ↑ Stolz D, Christ-Crain M, Bingisser R, et al. (January 2007). "Antibiotic treatment of exacerbations of COPD: a randomized, controlled trial comparing procalcitonin-guidance with standard therapy". Chest 131 (1): 9–19. DOI:10.1378/chest.06-1500. PMID 17218551. Research Blogging.
  12. ↑ 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. Research Blogging.

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