An Update on C-Reactive Protein for Intensivists (Report‪)‬

C-reactive protein (CRP) was first discovered in 1930 when a protein in the serum of patients with Streptococcus pneumoniae was found to precipitate and bind to the C-polysaccharide derived from the pneumococcal cell wall (1). It has been known for a long time that CRP is one of many non-specific acute phase reactants that are elevated during an inflammatory process. Because the CRP response to an inflammatory process is non-specific, many clinicians have not adopted its use as a predictive and prognostic test in intensive care medicine. Furthermore, the role of CRP as a predictor of infection, instead of inflammation, has become even more controversial since the introduction of procalcitonin as a test in this regard. Comparing CRP with other inflammatory markers such as procalcitonin can be difficult because of their different kinetics and many studies have looked at different types of patients (2). The overall evidence suggests that procalcitonin has much faster kinetics, both in its onset and offset, and may also be more specific than the CRP in diagnosing some infections (3-5). Because the CRP test is widely available and relatively cheap, it is likely to be widely used in many institutions in the foreseeable future. It is not the intention of this brief review to compare the advantages and disadvantages of CRP with the procalcitonin because this subject has been adequately reviewed (3,6), but to summarise our current knowledge on CRP as a marker of inflammation and partaker in diseases that are relevant to the practice of intensivists. This review aims to summarise the physiology of CRP, its potential roles and limitations as an inflammatory marker in intensive care medicine, and its emerging roles in the pathogenesis of some cardiovascular and autoimmune diseases. During the literature search for relevant articles in PubMed database before September 10, 2008, the following search terms, "C-reactive protein", "critically ill", "infection", "organ failure", "bacteraemia", "fungaemia", "sepsis", "cardiovascular disease" and "thromboembolism" were used without any language restrictions. Relevant references from the articles identified from the literature search were also retrieved for further analysis. Quantitative data of the studies were not pooled by meta-analytic techniques in this review because of the heterogeneity of patient characteristics and the disparate ways CRP were studied in the identified studies.