hs-CRP, CRP and ESR are all blood tests for inflammation, but they are used for different jobs. A standard CRP and an ESR help doctors find and follow significant inflammation, such as an infection or an autoimmune flare. An hs-CRP test measures the same protein as a standard CRP, with a method sensitive enough to read the low levels that relate to heart risk.
That is why only hs-CRP appears in heart risk guidance. A standard CRP is not built to separate the low values that matter for prevention, and ESR is an indirect measure that has a weaker link to heart disease.
Key takeaways
- hs-CRP and standard CRP detect one and the same protein, and the difference is how finely the test reads low values.
- ESR does not measure a protein at all. It times how quickly red blood cells settle in a tube.
- Heart risk categories exist for hs-CRP only.
- Even hs-CRP is a modest predictor, weaker than cholesterol or smoking.
- hs-CRP is part of both Cardio Res-Q assessments.
The three tests at a glance
| Test | What it measures | Mainly used for |
|---|---|---|
| hs-CRP | C-reactive protein, read precisely at low levels | Refining heart risk in people who are otherwise well |
| Standard CRP | C-reactive protein across a wide, higher range | Detecting and tracking infection or active inflammatory disease |
| ESR (sed rate) | How far red blood cells sink in a tube in one hour | Supporting diagnosis and follow-up of certain inflammatory conditions |
hs-CRP and CRP: one protein, two ranges
C-reactive protein is made by the liver when the body senses inflammation. During a serious infection it can climb to many times its resting level. A standard CRP test is tuned for that high range.
The levels linked to heart risk sit far lower, in the range where a standard test is too coarse to tell one person from another. The high-sensitivity version, hs-CRP, reads that low range reliably. It is not a different substance and not a heart-specific protein.
One practical trap: some labs report CRP in mg/dL and hs-CRP in mg/L. Those units differ tenfold, so check the units before comparing two reports.
ESR: the oldest and least specific
ESR stands for erythrocyte sedimentation rate. Blood is placed in a tall, thin tube, and the lab measures how far the red cells fall in an hour. Inflammation changes blood proteins in a way that makes red cells clump and sink faster.
It is an indirect signal, and many things move it besides inflammation. A review of the two tests concluded that both ESR and CRP lack sensitivity or specificity and should be used only in combination with a clinical history and physical exam. The same review noted that ESR and CRP commonly disagree with each other, particularly in chronic inflammatory diseases.1
ESR still earns its place in the workup of certain rheumatologic conditions. It is not a heart test.
Why only hs-CRP is used for heart risk
hs-CRP has been studied for this purpose on a large scale. A pooled analysis of 54 long-term studies with 160,309 people who had no history of vascular disease found that the risk of coronary heart disease rose steadily with CRP level. After adjusting for conventional risk factors, a threefold higher CRP level went with a risk ratio of 1.37. The authors cautioned that the association depended considerably on conventional risk factors and other markers of inflammation.2
From this kind of work came working categories. An hs-CRP below 1 mg/L is read as lower relative cardiovascular risk, 1 to 3 mg/L as average, and above 3 mg/L as higher.3 The 2018 US cholesterol guideline listed an hs-CRP of 2.0 mg/L or higher as a risk-enhancing factor.4 Our hs-CRP test guide explains how those numbers are applied.
ESR has been looked at too, and it came out weaker. In the Reykjavik Study, people in the top third for CRP had 1.45 times the odds of coronary heart disease of those in the bottom third, while the figure for ESR was 1.30.5 ESR does not appear among the risk-enhancing factors in the US cholesterol guideline.
How strong is hs-CRP, honestly?
It is a modest marker. In that same Reykjavik analysis, raised total cholesterol and cigarette smoking were both stronger predictors than CRP, and the authors called CRP a relatively moderate predictor of coronary heart disease.
The US Preventive Services Task Force concluded in 2018 that the evidence was insufficient to assess the balance of benefits and harms of adding hs-CRP to traditional risk assessment in adults without symptoms.6 So hs-CRP is best seen as one piece of supporting information. It can help tip an uncertain decision. It should not drive one alone.
It is also easy to misread. A recent infection, an injury or another short-term illness can push the result up for a while. See reasons hs-CRP runs high before reading too much into one value.
Which test answers which question
- "Is low-grade inflammation adding to my heart risk?" hs-CRP, measured when you are well, and ideally read next to ApoB, Lp(a) and your other risk factors.
- "Do I have an infection or an active inflammatory illness?" A standard CRP, often with an ESR, ordered by the doctor evaluating your symptoms.
- "Is my arthritis or other inflammatory condition under control?" Your specialist may follow CRP, ESR or both.
If you live with an inflammatory condition, your hs-CRP may run high for that reason. The condition itself can raise heart risk, which we cover in inflammation and heart disease.
hs-CRP in a Cardio Res-Q assessment
Both Cardio Res-Q assessments include hs-CRP among their inflammatory and vascular markers, together with homocysteine, ApoB, Lp(a) and metabolic labs. The Comprehensive Assessment is $775, and the Enhanced Assessment adds a CIMT ultrasound and a coronary calcium score.
Standard CRP and ESR are not on the published list of Cardio Res-Q labs. If you need those for symptoms, see your own doctor. If you have been ill recently, tell our team before your blood draw so the timing of your labs can be discussed. Read what to expect at your assessment, or visit the Cardio Res-Q program page.
Are You a Candidate for Cardio Res-Q?
Three quick questions about the risk factors we screen for. Your answers stay between you and the clinic.
Frequently asked questions
Can I use a regular CRP result to judge my heart risk?
Usually not. A standard CRP is designed for higher levels and may simply report a low result as "less than" a cutoff. The heart risk categories are based on hs-CRP.
Is hs-CRP specific to the heart?
No. It rises with inflammation anywhere in the body. It is used for heart risk because, in people who are otherwise well, a persistently higher level is linked with more cardiovascular events.
My ESR is high. Does that mean heart disease?
Not by itself. ESR is nonspecific and is affected by many things. A high ESR should be interpreted by the doctor who ordered it, in light of your symptoms.
Should hs-CRP be repeated?
If a result is high, it is often rechecked once you are well, because short-term illness can raise it. Your clinician decides the timing.
Related reading
This article is for general education and is not medical advice. Decisions about testing and medication should be made with your clinician. If you have chest pain or other symptoms of a heart attack, call 911.
