From the Guidelines
Your C-Reactive Protein (CRP) level of <5.0 mg/L is considered normal and indicates low levels of inflammation in your body. This result falls below the standard reference range of <10.0 mg/L, which is a positive finding 1. CRP is an acute phase protein produced by the liver in response to inflammation, infection, or tissue damage. When your body experiences inflammation, CRP levels rise rapidly, making it a useful marker for detecting inflammatory conditions.
Interpretation of CRP Results
According to a recent study published in Gastroenterology in 2023 1, a CRP level of <5 mg/L has a pooled sensitivity of 66.7% and a pooled specificity of 73.1% for detecting endoscopically active disease in patients with Crohn's disease. However, the GRADE certainty of evidence for this cutoff is VERY LOW, indicating significant uncertainty about the results.
Clinical Implications
Despite the normal CRP result, it is essential to consider other clinical findings and laboratory tests, especially if you had symptoms that prompted this test. The study found that a high proportion of symptomatic patients with endoscopic activity may be incorrectly classified as being in endoscopic remission based on a normal CRP level 1. Therefore, follow-up with your healthcare provider is crucial to determine the need for further testing or treatment.
Key Points to Consider
- CRP is just one marker of inflammation and should be interpreted alongside other clinical findings and laboratory tests.
- A normal CRP result does not rule out the presence of inflammatory conditions, especially in patients with symptoms suggestive of active disease.
- Further testing or treatment may be necessary, even with a normal CRP result, to ensure accurate diagnosis and management of underlying conditions.
From the Research
C-Reactive Protein (CRP) Overview
- CRP is a useful inflammatory marker with rapid kinetics during the inflammatory process 2
- Normal range for CRP is below 10.0 mg/L
Elevated CRP Levels
- CRP values above 500 mg/L are highly related to bacterial infections, with a high one-month mortality rate of 27% 2
- Elevated CRP levels are associated with improved treatment response to anti-inflammatory therapy in non-idiopathic pulmonary fibrosis fibrotic interstitial lung disease 3
Comparison with Other Inflammatory Markers
- Erythrocyte sedimentation rate (ESR) and CRP are frequently prescribed jointly, but their usefulness is uncertain 4
- The level of agreement between ESR and CRP is poor, with a kappa coefficient of 0.38 4
- CRP is a more reliable predictor of treatment response than ESR in certain subgroups of patients 3
Clinical Relevance of CRP
- CRP is a key modulator of atherosclerosis and a biomarker of the inflammatory response 5
- Elevated CRP levels are correlated with disease activity and functional severity in ankylosing spondylitis 6
- The treatment effect of NSAIDs/coxibs on CRP is relevant in patients with increased CRP at baseline 6