What is the difference between Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP)?

From the Guidelines

ESR and CRP are both blood tests that measure inflammation in the body, but they differ in important ways, with CRP being generally preferred for acute inflammation assessment due to its quicker response and higher specificity for inflammation and infection, as noted in a recent study 1. The key differences between ESR and CRP lie in their response times and specificities. CRP rises and falls more quickly than ESR, typically within 6-8 hours of an inflammatory stimulus and normalizing within days after resolution, making it ideal for monitoring acute inflammatory conditions 1. In contrast, ESR changes more slowly, taking 24-48 hours to rise and weeks to normalize, which makes it more reflective of chronic inflammatory states. Some of the key factors to consider when choosing between ESR and CRP include:

• The type of inflammation being assessed, with CRP being more suitable for acute inflammation and ESR for chronic inflammation
• The presence of non-inflammatory factors that can affect ESR, such as age, gender, anemia, and plasma protein levels
• The need for real-time information about disease activity, which CRP can provide, versus a more general assessment of chronic inflammation, which ESR can offer In clinical practice, CRP is particularly useful for bacterial infections, post-surgical monitoring, and assessing treatment response in conditions like rheumatoid arthritis, while ESR remains valuable for chronic conditions like temporal arteritis, polymyalgia rheumatica, and multiple myeloma 2, 1. The combination of ESR and CRP can provide complementary information about both acute and chronic inflammatory processes, and the American Academy of Orthopaedic Surgeons (AAOS) guidelines strongly recommend the use of ESR, CRP, and serum interleukin-6 testing for patients being assessed for peri-prosthetic joint infection 1. Some studies have also explored the use of other biomarkers, such as alpha-defensin, which has shown promise for diagnosing infection after total knee arthroplasty when combined with CRP 1. Overall, the choice between ESR and CRP depends on the specific clinical context and the type of inflammation being assessed, and both tests can be useful tools in the diagnosis and management of inflammatory conditions, as long as their limitations and potential biases are taken into account 2, 1.

From the Research

Differences between ESR and CRP

• ESR (Erythrocyte Sedimentation Rate) and CRP (C-Reactive Protein) are both markers of inflammatory conditions, but they have different uses and characteristics 3, 4.
• CRP is an acute-phase protein synthesized by the liver in response to inflammatory cytokines, and its measurement is widely used for the diagnosis and monitoring of inflammatory conditions, including sepsis, trauma, and malignancies 5.
• ESR, on the other hand, is an indirect measure of fibrinogen, which has a longer half-life than CRP, making it more helpful in monitoring chronic inflammatory conditions 3.
• CRP is more useful in diagnosis and monitoring responses to therapy in acute inflammatory conditions, such as acute infections 3.
• Many factors can result in falsely high or low ESR and CRP levels, and it is essential to consider these factors when interpreting test results 3, 4.

Clinical Applications

• ESR and CRP lack sensitivity and specificity, and therefore should be used only 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.
• Discrepancies between ESR and CRP measurements are common, particularly in chronic inflammatory diseases, and can be caused by various physiological factors, including noninfectious conditions and resolution of inflammation 4.

Test Utilization

• CRP is a more sensitive and specific test for detecting acute phase inflammation, and the American Society for Clinical Pathology recommends ordering CRP rather than ESR to detect acute phase inflammation in patients with undiagnosed conditions 6.
• Education, clinical decision support, and audit and feedback can help reduce unnecessary use of ESR testing and promote appropriate utilization of laboratory tests for inflammation 6.