hs-CRP: inflammation and heart risk, and why infection distorts it

Heart disease is not only a cholesterol problem. Inflammation plays a part at every stage, from the first deposit in an artery wall to the rupture of a plaque that causes a heart attack. hs-CRP is a simple blood test that gives a window into that background inflammation.

What CRP is

C-reactive protein, or CRP, is made by the liver in response to inflammation anywhere in the body. During an infection or after an injury it can rise quickly to very high levels, then fall again as you recover. A standard CRP test is designed to pick up these large rises.

The high sensitivity test, hs-CRP, measures the same protein but accurately detects much lower levels. At these low levels, CRP reflects chronic, low grade inflammation rather than an acute illness, and that is what is linked to heart risk.

The risk bands

LifePrint uses the bands set out in the American Heart Association and Centers for Disease Control and Prevention (AHA/CDC) 2003 scientific statement, in mg/L:

• Below 1 mg/L: lower cardiovascular risk.
• 1 to 3 mg/L: average risk. This is shown in LifePrint's grey zone.
• Above 3 mg/L: higher cardiovascular risk.

These bands describe risk relative to other people. hs-CRP adds to, but does not replace, the traditional risk factors: cholesterol, blood pressure, smoking, diabetes, age and family history. It is most useful for people whose risk is borderline, where it can help tip the decision one way or the other.

Why infection distorts it

Because CRP rises so sharply with acute illness, a single high reading taken while you are fighting something off tells you about that illness, not your heart. Even a mild cold, a dental infection, a flare of an old injury or a hard training block can push it up.

For the same reason, it is best to book your blood test at least two weeks after recovering from any illness, unless your doctor asks for a test during it.

What else raises hs-CRP

• Excess body fat, especially around the middle, which is one of the most common causes of a mildly raised level.
• Smoking.
• Insulin resistance and type 2 diabetes.
• Poor sleep and sleep apnoea.
• Chronic inflammatory conditions, such as rheumatoid arthritis, inflammatory bowel disease, psoriasis and gum disease.
• Oral contraceptives and hormone therapy containing oestrogen.
• Pregnancy.
• Recent hard exercise, surgery or injury.

Some medicines, including statins, lower hs-CRP. If you take one, tell us so your result can be read in context.

Bringing it down

A mildly raised hs-CRP often responds to the same steps that improve heart health in general. Losing excess weight is the single most effective. Regular activity, stopping smoking, better sleep, a diet rich in vegetables, legumes, whole grains, nuts and oily fish, and less alcohol all help. Treating gum disease and managing any chronic inflammatory condition can also lower it.

Many supplements claim to reduce inflammation. The evidence that they lower heart risk is weak. Speak to your doctor before taking any of them.

Reading hs-CRP with the rest of your results

On the Heart and Metabolic panel, hs-CRP sits alongside your lipids, ApoB, Lp(a), blood sugar and insulin. A raised hs-CRP next to high triglycerides, a raised fasting insulin and a raised ALT points towards insulin resistance and fatty liver as the likely driver. A raised hs-CRP with an otherwise clean metabolic picture is more likely to reflect a recent illness or another source of inflammation, and a repeat is the sensible next step.

hs-CRP is also part of the Essentials panel. If your result is above 3 mg/L on two occasions, or above 10 mg/L, discuss it with a registered healthcare practitioner. Your LifePrint report is health information, not a diagnosis.