Erythrocyte Sedimentation Rate and C-Reactive Protein: Effective Testing of Inflammation

Jane M. Caldwell, Ph.D. and Aisha M. David, M.D.

Inflammation Markers

Inflammation markers are typically detected during the initial laboratory screening of patients suspected of having acute inflammation caused by an underlying disease or condition. The erythrocyte sedimentation rate (ESR) is the most common test, useful as a general indicator of inflammation. In addition to being a screening test, it is regularly performed in monitoring patients for the presence of autoimmune and infectious diseases. The erythrocyte sedimentation rate in patient samples helps determine the severity of inflammation and the effectiveness of treatment. ESR may be elevated in systemic and orthopedic infections, bronchiolitis, giant cell arteritis, kidney and coronary artery diseases, autoimmune diseases, vasculitis, and in some types of cancer.

C-reactive protein (CRP) is another common serological biomarker of systemic inflammation. Besides inflammation, this protein is involved in the immune system's response to bacterial and fungal infections, autoimmune and cardiovascular diseases. Since CRP levels rise significantly more in bacterial infections than in viral ones, it also helps clinicians determine the appropriateness of prescribing antibiotics. ESR and CRP are the most common tests for the primary screening of inflammatory conditions.

Clinical Use of ESR and CRP

Determining ESR and CRP are nonspecific screening tests and therefore do not have high individual specificity, and neither should be used alone to exclude a clinically established diagnosis. Both tests are useful as adjunct methods in the diagnosis and monitoring of both acute and chronic inflammatory conditions, such as injuries, infections, infarcts, neoplasms, and systemic autoimmune diseases, including inflammatory arthritis. They are most beneficial when there is a high or low clinical probability of disease.

A retrospective cohort study showed a discrepancy between ESR and CRP values in 12.5% of patients. These discrepancies may be related to the duration of the acute phase (CRP rises earlier than ESR in inflammation) or other non-inflammatory conditions (for example, elevated ESR with normal CRP, which is often seen in some malignant neoplasms). Using both tests simultaneously provides more detailed diagnostic information.

Examples of Dual Marker Use

The level of CRP is proportional to the intensity of inflammation and is very sensitive to minor changes during acute reactions. Due to its short half-life and rapid kinetics, CRP quickly decreases after inflammation resolves, making it useful as a measure of treatment response. In contrast, ESR is significantly influenced by sex (higher levels in women), kidney disease, and age (especially after 60 years).

High ESR along with low CRP can help identify low-differentiated bone infection or is a useful indicator for monitoring patients with systemic lupus erythematosus. Regarding the cardiovascular system, individuals with high ESR/low CRP are more frequently diagnosed with ischemic stroke or transient ischemic attack, while low ESR/high CRP is more commonly observed in myocardial infarction and venous thromboembolism.

Elevated ESR has proven to be a better predictor of treatment outcomes in the early stages of rheumatoid arthritis (RA), while CRP is a better marker in the later stages.

ESR Method and Test Turnaround Time

The Westergren ESR test, developed in 1921 and recommended by ICSH, is a classic manual method for measuring sedimentation rate in a tube over one hour. However, the manual method is labor-intensive, operator-dependent, and influenced by environmental factors (temperature, vibration, angle of the tube). ESR testing has become much more convenient with the advent of automated systems directly at the patient's side (POC). Testing time is reduced from 1 hour to a few minutes (3 minutes for the first sample and 15-20 seconds for each subsequent one). New POC devices also eliminate biological risks by working with closed systems and using EDTA tubes.

Cost-Effectiveness of ESR and CRP

Automated ESR determination using modern systems (e.g., the iSED line from ALCOR Scientific) reduces the laboratory technician's practical work time by 96% and total turnaround time by 87% compared to the manual method. The cost of one test for the laboratory is only about $2.00, making it extremely cost-effective. In combination with CRP analysis, ESR remains a reliable and indispensable clinical tool.

Educational support for this article was provided by ALCOR Scientific.