Inflammation
C-reactive protein
C-reactive protein is an acute-phase protein made by the liver that rises within hours of tissue injury, infection or inflammation. At the point of care it is widely measured from a fingerprick to support antibiotic stewardship and to gauge the presence and broad intensity of an inflammatory response.
Why it is measured
CRP responds quickly and predictably to inflammation, so a near-patient result can help distinguish likely bacterial from self-limiting illness and can support, alongside clinical assessment, decisions on whether antibiotics are warranted. It is also tracked serially to follow how an inflammatory or infective process is settling.
| Typical range | Indicative adult guide: under 5 mg/L is commonly regarded as normal, and many laboratories treat under 10 mg/L as unremarkable. For cardiovascular risk stratification the high-sensitivity (hs-CRP) bands are often quoted as under 1 mg/L (lower), 1 to 3 mg/L (intermediate) and over 3 mg/L (higher). Primary-care respiratory pathways frequently use thresholds around under 20, 20 to 100 and over 100 mg/L to frame antibiotic decisions. Values vary by method, analyser and population, so always interpret against the issuing laboratory's stated range. |
|---|---|
| Sample | Capillary (fingerprick) whole blood, typically around 10 to 20 microlitres; venous whole blood, serum or plasma are also accepted on many analysers. |
| Turnaround | Approximately 2 to 4 minutes from sample application on most point-of-care systems. |
Point of care devices that report it
- Aidian QuikRead go CRP (and wrCRP wide-range variant)
- Abbott Afinion CRP
- LumiraDx CRP Test
- Radiometer AQT90 FLEX CRP
- Boditech ichroma CRP
- Eurolyser CRP (CUBE / smart analysers)
- Horiba Microsemi CRP
Questions, answered
How does point-of-care CRP support antibiotic decisions?
A near-patient CRP result, used together with the full clinical picture, can help indicate whether an illness is more likely to be a significant bacterial infection or a self-limiting one. Lower results generally make a serious bacterial cause less likely while higher results raise that probability, which supports antibiotic stewardship. It is a decision aid only and does not replace clinical judgement, local guidelines or, where relevant, further testing.
What is the difference between standard CRP and high-sensitivity CRP (hs-CRP)?
They measure the same protein but over different ranges and for different purposes. Standard CRP is used for infection and inflammation where values can climb into the tens or hundreds of mg/L, whereas hs-CRP resolves very low concentrations and is used mainly for cardiovascular risk stratification. Many point-of-care analysers offer a wide measuring range that can serve both needs, so the assay variant and its reportable range should be checked before interpreting a result.
Why can CRP results differ between a point-of-care device and the main laboratory?
Differences arise from the measurement method, calibration, sample type (capillary versus venous) and each method's reportable range and precision, particularly at very low or very high values. Good agreement is reported for several point-of-care systems, but results are best trended on the same method where possible and interpreted against the range supplied with that specific analyser. Routine quality control and external quality assessment help keep point-of-care and laboratory results aligned.