From the Guidelines
Elevated C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR) are primarily caused by inflammation or infection in the body, as supported by the most recent study 1. These are non-specific inflammatory markers that increase in response to various conditions. Common causes include:
- Bacterial infections (like pneumonia, urinary tract infections, or cellulitis)
- Viral infections
- Autoimmune disorders (such as rheumatoid arthritis, lupus, or inflammatory bowel disease)
- Tissue injury or trauma
- Recent surgery
- Certain cancers (particularly lymphomas) Chronic inflammatory conditions like obesity, smoking, and cardiovascular disease can also lead to persistent elevation of these markers. The elevation occurs because inflammation triggers the liver to produce acute phase proteins like CRP, while ESR increases due to changes in plasma proteins that cause red blood cells to stack together and settle more quickly. The degree of elevation often correlates with the severity of inflammation, with CRP typically rising and falling more rapidly than ESR in response to changes in inflammation. When these markers are elevated, further diagnostic testing is usually needed to determine the specific underlying cause, as suggested by 1 and 1.
Some key points to consider:
- CRP and ESR can be elevated in various conditions, making them non-specific markers
- The degree of elevation can indicate the severity of inflammation
- Further testing is necessary to determine the underlying cause of elevated CRP and ESR
- Chronic inflammatory conditions can lead to persistent elevation of these markers
- Recent studies, such as 1 and 1, support the use of CRP and ESR as markers of inflammation, but also highlight the need for careful interpretation and further testing to determine the underlying cause.
In clinical practice, it is essential to consider the patient's overall clinical presentation, medical history, and other laboratory results when interpreting elevated CRP and ESR levels, as recommended by 1 and 1.
From the Research
Causes of Elevated CRP and ESR
Elevated C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR) are markers of inflammatory conditions. Several factors can contribute to elevated levels of these markers, including:
- Infections, such as acute infections 2
- Chronic inflammatory conditions, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and osteoarthritis (OA) 3
- Noninfectious conditions, such as resolution of inflammation 4
- Physiological factors, such as fibrinogen levels, which can affect ESR measurements 2
- Immunoglobulins, rheumatoid factor (RF), and hemoglobin, which can affect ESR measurements 5
Factors Affecting ESR and CRP Measurements
Several factors can affect ESR and CRP measurements, leading to falsely high or low levels, including:
- Half-life of fibrinogen, which is longer than CRP, making ESR more useful for monitoring chronic inflammatory conditions 2
- Discordance between ESR and CRP measurements, which can occur in certain settings, such as chronic inflammatory diseases 4
- Non-acute phase factors, such as immunoglobulins and RF, which can affect ESR measurements 5
Clinical Application of ESR and CRP
ESR and CRP are widely used laboratory markers of systemic inflammation, but they lack sensitivity and specificity. Therefore, they should be used in combination with clinical history and physical exam for diagnosis and monitoring of pathological conditions 4. The clinical application of these tests is best applied to conditions in which there is high or low clinical probability of disease 4. CRP appears to be a better measure of the acute phase response, while ESR may measure general severity better than CRP 5. The combination of ESR and CRP yields useful information that is often not apparent when only a single test is used 5.