Inflammation and immunity · Blood

CRP

A protein that rises quickly with inflammation or infection; shows whether there is inflammation somewhere, not where or why.

At a glance

Measured in blood
In 6 test panels
No special preparation

Explanation

CRP: what is measured?

CRP (C-reactive protein) is a protein that the liver makes in response to inflammation or infection. Within 6 to 8 hours after inflammation starts, the level in the blood rises sharply, and after recovery it falls quickly again, usually within a few days. This makes CRP suitable for showing acute inflammation and following its course. The value says nothing about where the inflammation is.

What can it detect?

Acute infections, especially bacterial infections such as pneumonia
Inflammatory diseases, such as rheumatoid arthritis or an inflammatory bowel disease
Tissue damage after surgery, an injury or a heart attack
The course of an inflammation and the effect of its treatment

Result

What does the result mean?

CRP too high

A raised CRP points to inflammation or infection somewhere in the body. In bacterial infections, such as pneumonia, the value often rises above 100 mg/L; in viral infections the rise usually stays limited. Surgery, an injury and an inflammatory disease such as rheumatism also raise CRP. A slightly raised value is not very specific and also occurs with a cold, overweight, smoking or gum inflammation. Symptoms that go with inflammation are fever, pain, swelling or feeling ill. Rarely: a tumor.

CRP too low

A low or unmeasurable CRP is normal. A low value makes an acute bacterial infection or an active inflammatory disease unlikely, but does not rule it out completely: in the first hours of an infection CRP has not yet risen, and in some diseases, such as lupus or a small local inflammation, the value stays low.

After an abnormal result

The GP assesses CRP together with the symptoms and the physical examination. A slightly raised value without a clear cause is usually repeated after a few weeks; with a strongly raised or persistently raised value, targeted tests follow to find the source of the inflammation, for example a urine test, a chest X-ray or a referral.

Reliability

How reliable is the test?

CRP is a sensitive but non-specific inflammation marker: a raised value says there is inflammation, not where it is or what causes it. According to the Dutch Society for Clinical Chemistry (NVKC), CRP is mainly useful to make a serious bacterial infection more or less likely and to follow the course; the value can only be interpreted together with symptoms and a physical examination. For inflammation, CRP is preferred over the erythrocyte sedimentation rate (ESR), because CRP responds faster and is less easily disturbed.

What can affect the result?

In the first 6 to 12 hours of an infection CRP is still low; a measurement taken too early can give false reassurance.
Overweight, smoking, pregnancy, heavy exercise and small inflammations such as gum inflammation give a slightly raised value without disease.
Anti-inflammatory drugs such as corticosteroids and biologicals (for example for rheumatism) can suppress the rise in CRP.
The standard CRP test does not measure low values (below 3 to 5 mg/L) accurately; estimating cardiovascular risk requires the more sensitive hs-CRP.

Who it is for

Who is the test useful for?

Useful for

Useful with symptoms that fit an infection or inflammation, such as fever, coughing with shortness of breath, abdominal pain, joint symptoms or long-lasting tiredness with feeling ill, and to follow the course of a known inflammatory disease. In adults without symptoms and without a reason, a CRP yields little: a normal value says little and a slightly raised value is usually harmless. The standard CRP test is not suitable for estimating cardiovascular risk.

How common is it?

A raised CRP is not a disease but a signal. Infections are the most common cause and are among the most common reasons for a visit to the GP, especially in winter. Chronic inflammatory diseases such as rheumatoid arthritis are less common. There are no Dutch figures on how often a raised CRP is found as an isolated finding.

NVKC, allesovertesten.nl

Drawbacks and risks

CRP does not show a location or cause; a slightly raised value without symptoms often leads to follow-up tests that find nothing.
A normal CRP early in an infection can give false reassurance.

Get tested

CRP: test panels

CRP is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
CRP
Your risk of cardiovascular disease with our CRP blood test – an essential marker for inflammation and heart health.
€ 23,00
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General Health Checkup
With this General Health Check-up, you gain detailed insight into your overall health and well-being.
€ 125,00
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PhenoAge
PhenoAge Biological Age Test; determine your biological age with 9 standard blood values.
€ 85,00
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Comprehensive Blood Test
Comprehensive blood test covering blood count, thyroid, kidney and liver function, glucose, inflammation markers and cholesterol.
€ 215,00
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Inflammation Basic
CRP, leukocytes, and ESR. Detects and monitors inflammations, infections, and autoimmune diseases.
€ 78,00
Blood draw
Inflammation Extensive
CRP, leukocytes, ESR, and platelets. Extensive test for diagnosis and monitoring of chronic inflammation and autoimmune diseases.
€ 101,00

How reliable is the test?

CRP