ESR (erythrocyte sedimentation rate)
Also known as: sed rate, erythrocyte sedimentation rate, sedimentation rate
An old but still useful test that measures how far red blood cells settle in a narrow tube in one hour. Inflammatory proteins such as fibrinogen and immunoglobulins make red cells stack and sink faster, so the ESR rises with inflammation, infection and some blood disorders, more slowly and less specifically than CRP.
- Canonical name
- Erythrocyte sedimentation rate
- Abbreviations
- ESR
- Kind
- Laboratory test
- Categories
- Immunology & inflammation, Blood & haematology
- Specimen
- Whole blood (EDTA)
- Method
- Automated cell counter
- Terminology
- LOINC 30341-2
- Type
- Blood test
- Sample
- Blood from a vein
- Used for
- Inflammatory disease, giant cell arteritis, myeloma, monitoring
- Measures
- How quickly red cells settle, a proxy for inflammatory proteins
- Result
- Numeric (mm/h); reference limit rises with age
Why is it used?
- Suspected temporal (giant cell) arteritis and polymyalgia rheumatica, where it is part of the diagnostic picture
- Monitoring rheumatoid arthritis, lupus and other long-term inflammatory diseases
- Suspected myeloma and other conditions that raise immunoglobulins
- Unexplained symptoms where inflammation is one possibility, alongside CRP
What does it measure?
| Component | What it measures | A higher value may be seen in | A lower value may be seen in |
|---|---|---|---|
| Sedimentation rate ESR | Red-cell settling distance in one hour | Inflammation, infection, anaemia, pregnancy, myeloma, older age, kidney disease | Polycythaemia, sickle cell disease, very high white-cell counts (low or falsely low) |
A high or low value can be associated with several different situations; the result is interpreted with other results, symptoms, history and clinical findings.
How is it performed?
A venous blood sample in an anticoagulant tube, tested within a few hours.
Specimen. Venous blood in an EDTA or citrate tube
Do I need to prepare?
None.
What do the results generally mean?
| Finding | What it may indicate |
|---|---|
| Markedly raised ESR (over 100 mm/h) | Giant cell arteritis, myeloma, serious infection or widespread cancer are among the causes considered |
| Raised ESR with raised CRP | Active inflammation or infection |
| Raised ESR with normal CRP | Anaemia, pregnancy, kidney disease, lupus, myeloma or simply older age |
| Normal ESR | Makes active inflammatory disease less likely but does not exclude it; the ESR is slow to rise |
What can affect the result?
- Anaemia and red-cell shape (sickle cells settle slowly)
- Pregnancy, age and sex
- Time between sampling and testing
- High immunoglobulin or fibrinogen levels from any cause
Medicines. Corticosteroids and anti-inflammatory biologics lower it; oral contraceptives and some intravenous immunoglobulin preparations raise it.
What can the test not tell you?
- What is causing the inflammation
- How recently the inflammation began (it lags by days)
- Whether a normal result excludes disease
The ESR is influenced by many things other than inflammation, including anaemia, red-cell shape, pregnancy, age and immunoglobulin levels, and it changes slowly. CRP is preferred for tracking acute infection; the ESR keeps a place in a few conditions and in long-term monitoring.