Although Shakespeare did not have this question in mind when he wrote Hamlet, it is an appropriate one to consider when completing a laboratory test requisition. C-reactive protein (CRP) is one of the most sensitive acute phase proteins and appears to be a nonspecific host defense against inflammation. The difference between CRP and hs-CRP is contained in the “hs” abbreviation; “high sensitivity”. CRP is traditionally measured down to concentrations of 3-5 mg/L, whereas through changes in detection systems, hs-CRP measures down to concentrations around 0.3 mg/L.
This 10-fold improvement in sensitivity allows hs-CRP to be used to detect low levels of chronic inflammation, which has been associated with coronary artery disease, cerebrovascular disease, and other peripheral vascular disease. Low levels of chronic inflammation have been identified as an important component in the development and progression of atherosclerosis.
CRP can be used in assessing the activity of inflammatory disease (e.g. rheumatoid arthritis and Crohn’s disease) and other tissue destructive processes. However, it is not sensitive enough to measure those low levels of chronic inflammation associated with atherosclerosis.
“To be, or not to be specific in ordering CRP/hs-CRP, that is the question.”