CRP as an aid in the diagnosis of sepsis

CRP is a well-established biomarker of infection, inflammation, and sepsis and is widely used in clinics and emergency departments

CRP is a well-established biomarker of infection and inflammation.

Because the levels of CRP rise much more significantly during acute inflammation than the levels of the other acute phase reactants, the CRP test has been used for decades to indicate the presence of systemic inflammation, infection, or sepsis.

Although its low specificity may be its primary drawback as a biomarker of sepsis in adults, it is commonly used to screen for early onset sepsis (occurring during the first 24 hours of life) because its sensitivity is generally considered to be very high in this setting [1].

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CRP as an aid in the diagnosis of sepsis

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Aiding diagnosis of sepsis with a CRP blood test

Because of the non-specific nature of the acute-phase response and the resulting rise in CRP levels, CRP cannot be used alone to diagnose any condition [2].

CRP can, however, provide supportive evidence for diagnosis of several infections, such as sepsis. For instance, when certain criteria are present, such as high fever and increased respiratory rate, CRP values can be used to diagnose an inflammatory condition or infection, which could develop into sepsis [2].

CRP in combination with a procalcitonin (PCT) test can effectively distinguish systemic inflammation from sepsis [2]. Sepsis is the result of an uncontrolled immune-response to infection and has a mortality rate close to 30 % [3].

CRP, PCT and lactate or a combination of these biomarkers correlate with the severity of the infection and offer prognostic value around the clinical course of the patient [2, 4].

If the lactate concentration exceeds 2.0 mmol/L, it is a sign of severe organ hypoperfusion, which may lead to septic shock with a mortality rate of around 50 % [3-5].

References

1. Faix J. Biomarkers of sepsis. Crit Rev Clin Lab Sci. 2013 Jan; 50(1): 23-36.
2. Castelli FP, et al. Procalcitonin and C-reactive protein during systemic inflammatory response syndrome, sepsis and organ dysfunction. Crit Care 2004; 8(4):234-42
3. Brun-Buisson C. The epidemiology of the systemic inflammatory response. Intensive Care Med. 2000, Vol.26 Suppl 1: 64-74.
4. Freund Y, et al. Serum lactate and procalcitonin measurements in emergency room for the diagnosis and risk-stratification of patients with suspected infection. Biomarkers 2012; 17(7): 590-6
5. Bakker J, et al. Serial blood lactate levels can predict the development of multiple organ failure following septic shock. Am J Surg 1996; 171: 221-6.

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