High values of this 'inflammatory marker' CRP are associated with inflammation from some cause, such as infection or arthritis. It is not an exact test, it is also nonspecific. Very high readings are associated with polymyalgia rheumatica, a painful muscle ache affecting usually the upper arms or legs, and temporal arteritis - inflammation of the temporal artery which usually presents with severe headache in the temple area.

The High Sensitivity version of this test (HiS CRP) has the added value of acting as a measure of low-level inflammation which can, alongside other markers, be used to assess the risk of cardiovascular and peripheral vascular (heart and blood vessel) disease.