CRP
What it measures, and what changes the number.
CRP, or C-reactive protein, is a protein made by the liver as part of the body's response to inflammation, infection and tissue injury. It is known as an acute phase protein because its concentration can change within hours.
It is often ordered with ESR and a white blood cell count, since all three reflect inflammatory activity in different ways and over different time scales. Ferritin, another acute phase protein, may appear on the same report.
Standard CRP and hs-CRP measure the same protein, but the high-sensitivity assay is designed to detect much smaller amounts, so the two are listed separately. Fasting has little effect, but a recent cold, infection, injury or hard exercise can influence the result, which is why the timing relative to illness matters when comparing results. Labs may print it as Proteína C Reactiva en suero.
Often read alongside: hs-CRP, ESR (1h), White blood cells, Ferritin