What is Erythrocyte Sedimentation Rate (ESR)?
The erythrocyte sedimentation rate (ESR), also known as "sed rate," is a blood test that measures how quickly red blood cells settle to the bottom of a test tube over time, serving as a nonspecific marker of inflammation and systemic illness. 1, 2
How the Test Works
- ESR measures the rate at which red blood cells (RBCs) fall in an upright test tube containing anticoagulated whole blood. 2
- Normally, negative charges keep RBCs separated, but when acute phase proteins (particularly fibrinogen and immunoglobulins) increase during inflammation, these charges are neutralized. 3, 2
- RBCs then stack into chains called "rouleaux" and sediment more rapidly. 2
- The Westergren method is the most commonly used technique, measuring the distance RBCs fall in millimeters per hour (mm/h). 4, 2
Normal Reference Values
- Normal ESR ranges from approximately 1-8 mm/h in healthy adults, though values vary significantly by age and sex. 5
- ESR is typically higher in females than males (approximately 2-fold difference). 6
- ESR increases steadily with age, with individuals over 65 years having approximately 2-fold higher values than those aged 18-35 years. 6
- Traditional cutoffs define elevated ESR as >20 mm/h in men and >30 mm/h in women. 4
Clinical Significance and Interpretation
ESR is most valuable for diagnosing and monitoring specific chronic inflammatory conditions rather than as a general screening test. 3, 7
Conditions Where ESR is Particularly Useful:
- Giant cell arteritis (temporal arteritis): ESR >40 mm/h has high sensitivity (93.2%) for diagnosis. 4
- Polymyalgia rheumatica: ESR remains a key diagnostic and monitoring tool. 3, 7
- Acute rheumatic fever: ESR >60 mm/h is typical, and normal values should prompt reconsideration of the diagnosis (except in isolated chorea). 4
- Rheumatoid arthritis: Useful for diagnosis and follow-up. 3, 8
- Multiple myeloma, septic arthritis, and osteomyelitis: ESR aids in diagnosis. 3, 8
Extremely Elevated ESR (≥100 mm/h):
- Strongly associated with serious underlying disease, most commonly pulmonary infections (58% of infectious cases), hematopoietic stem cell diseases (45.7% of hematologic cases), and diffuse connective tissue diseases (75.7% of autoimmune cases). 9
- Other major causes include lymphocyte/plasma cell diseases, metastatic malignancy, and collagen vascular disease. 7, 9
Factors That Influence ESR
Factors That Increase ESR:
- Anemia, macrocytosis, and hypoalbuminemia elevate ESR independent of inflammation. 3
- Increased fibrinogen levels (positively correlated, ρ = 0.345). 9
- Obesity and metabolic syndrome. 6
- Smoking. 6
Factors That Decrease ESR:
- Polycytemia, microcytosis, and fibrinogen consumption lower ESR values. 3
- Higher hemoglobin, RBC count, and hematocrit (all negatively correlated). 9
- Regular physical activity. 6
- Light alcohol consumption (compared to abstainers). 6
Limitations and Clinical Context
- ESR should NOT be used for routine screening in asymptomatic patients, as it lacks specificity. 3
- ESR rises and falls slowly (over 48 hours) compared to C-reactive protein (CRP), making it better suited for monitoring chronic conditions rather than acute infections. 2
- In acute disease states, CRP and procalcitonin are preferred over ESR. 3
- ESR does not consistently correlate with CRP levels (ρ = -0.019). 9
- Technical factors (temperature, time from collection, tube orientation) can affect results. 2