Empeiria

C-reactive protein

Also known as CRP, C-reactive protein, inflammation marker

protein · no single molecular formula

LOINC 1988-5 code verified serum mg/L

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

A protein your liver makes whenever there is inflammation anywhere in your body. It rises within hours and falls just as quickly.

Hepatically synthesized acute-phase pentraxin, rising within hours of an inflammatory stimulus and falling as rapidly once it resolves.

why measured unverified

It answers one question well: is there inflammation right now. It never says where or why.

It answers one question well: is there inflammation right now. It never says where or why.

No clinical version written yet.

if high unverified

Something inflammatory is going on. An ordinary infection, a recent injury or recent surgery all do it. It cannot distinguish a chest infection from a flare of arthritis.

Something inflammatory is going on. An ordinary infection, a recent injury or recent surgery all do it. It cannot distinguish a chest infection from a flare of arthritis.

No clinical version written yet.

caveats unverified

Its main use here is as context for other results. Ferritin rises with inflammation too, so a normal ferritin alongside a high CRP may still be hiding an iron shortage.

Its main use here is as context for other results. Ferritin rises with inflammation too, so a normal ferritin alongside a high CRP may still be hiding an iron shortage.

No clinical version written yet.

What this substance is

A pentameric 115 kDa protein; measured as mass, not structure.

UniProt P02741 · PDB 1B09

3D model · Protein (PDB 1B09)

C-reactive protein: five identical chains in a ring (PDB 1B09). Experimental structure from the Protein Data Bank, entry 1B09, shown as its biological assembly (5 chains). Every chain was checked against its UniProt sequence (at least 100.0% identical). Drag to rotate, scroll to zoom.

Reference ranges

Checking your own result against this range needs the running application; this is a static copy. Nothing you type anywhere in Empeiria is ever sent to a server.

This open edition shows a range only where a public-domain or openly licensed source states one, and none does for this marker yet. Compare your result with the range printed on your own lab report.

How it is measured

In practice

A health worker takes a small blood sample from a vein in your arm with a needle. It usually takes less than five minutes. Some medicines can change the result, so tell your provider what you take. Do not stop a prescribed medicine unless your provider says so.

Venous blood sample by venipuncture. Medications and supplements, including magnesium and NSAIDs such as ibuprofen and aspirin, may affect results and should be disclosed; prescription medicines should not be stopped without the provider's advice. Standard CRP is distinct from high-sensitivity CRP (hs-CRP), which detects very small increases and is used to estimate cardiovascular risk.

Before the test

  • Tell your provider about all medicines and supplements, including magnesium, ibuprofen and aspirin.
  • Do not stop prescription medicines without talking with your provider first.

Where: laboratory

Source: C-Reactive Protein (CRP) Test, MedlinePlus (U.S. National Library of Medicine) cited · not yet checked by a person

In the lab

immunoturbidimetric

Latex-enhanced immunoturbidimetry

Tiny particles coated in antibodies clump together when CRP is present. The cloudier the sample becomes, the more CRP there was.

Antibody-coated latex particles agglutinate in the presence of CRP, and the resulting turbidity is measured.

  • Read by: Turbidity at 546 nm
Why labs disagree: Standard and high-sensitivity CRP measure the same molecule but are used for different jobs. hs-CRP is designed to pick up very small increases and is used to estimate heart disease risk; a standard CRP test is used to gauge inflammation, such as from an infection, where levels are high. Results from the two are judged against different cut-offs.

Sources: C-Reactive Protein (CRP) Test, MedlinePlus (U.S. National Library of Medicine); NHANES 2017-2018 Laboratory Procedure Manual: High-Sensitivity C-Reactive Protein, CDC/NCHS cited · not yet checked by a person

What it reports on

Associated symptoms

When high

Conditions this marker features in

When high
  • high A cluster of risks that travel together · supportive
    Often raised, reflecting low-grade inflammation; it rises with the number of syndrome features.
  • high Anaemia caused by long-term illness · supportive
    Signs of inflammation, such as a raised CRP, are expected and support the diagnosis. CRP is one of the tests used to work it up.
  • high Gout · supportive
    Raised during a flare. CRP shows inflammation, but not what is causing it.
Either direction

Ordered as part of

iron_studies · metabolic_risk