What is the ESR Test?
The Erythrocyte Sedimentation Rate (ESR) test measures how quickly red blood cells settle to the bottom of a test tube over one hour. When there is inflammation in the body, certain proteins (such as fibrinogen and immunoglobulins) increase in the blood, causing red blood cells to clump together and settle faster.
The ESR is a simple, inexpensive, and widely used test. It does not diagnose a specific disease but indicates that inflammation is present somewhere in the body.
Why is This Test Done?
- To detect and monitor inflammation in the body
- To help diagnose autoimmune diseases (rheumatoid arthritis, lupus, polymyalgia rheumatica)
- To screen for and monitor infections, including tuberculosis (TB) which remains common in Sri Lanka
- To monitor the activity of chronic inflammatory conditions
- To help investigate unexplained fever, joint pain, or weight loss
- To assess response to treatment for inflammatory or infectious diseases
How to Prepare for the ESR Test
Simple Preparation
- No fasting required. You can eat and drink normally before the test.
- The test can be done at any time of the day.
- Inform your doctor if you are taking anti-inflammatory medications (ibuprofen, aspirin, steroids) as they can lower ESR.
- Mention if you are pregnant, as ESR is naturally elevated during pregnancy.
Understanding Your Results
ESR normal ranges vary by age and gender. The following table provides general reference ranges:
| Category | Normal ESR (mm/hr) |
|---|---|
| Males (under 50 years) | 0 - 15 mm/hr |
| Males (over 50 years) | 0 - 20 mm/hr |
| Females (under 50 years) | 0 - 20 mm/hr |
| Females (over 50 years) | 0 - 30 mm/hr |
| ESR Level (mm/hr) | Interpretation | Possible Causes |
|---|---|---|
| Within normal range | No significant inflammation | Healthy state |
| 20 - 40 mm/hr | Mildly elevated | Mild infection, pregnancy, anaemia, ageing, mild inflammatory conditions |
| 40 - 100 mm/hr | Moderately elevated | Active infection (TB, pneumonia), active autoimmune disease, significant inflammation, some cancers |
| Above 100 mm/hr | Severely elevated | Severe infection, multiple myeloma, temporal arteritis, advanced malignancy, TB with complications. Requires urgent evaluation. |
Common Conditions Associated with Elevated ESR
- Rheumatoid arthritis: ESR is commonly used to monitor disease activity and response to treatment.
- Tuberculosis (TB): A very common cause of elevated ESR in Sri Lanka. ESR helps in monitoring treatment response over months.
- Infections: Bacterial infections, abscesses, bone infections (osteomyelitis), and urinary tract infections can all raise ESR.
- Cancers: Lymphoma, multiple myeloma, and other malignancies can cause significantly elevated ESR.
- Polymyalgia rheumatica: An inflammatory condition in older adults with very high ESR (often above 40-50 mm/hr).
- Systemic lupus erythematosus (SLE): ESR rises during active flares.
ESR vs CRP: What is the Difference?
Both ESR and CRP are markers of inflammation, but they behave differently:
| Feature | ESR | CRP |
|---|---|---|
| Speed of change | Rises slowly (days) and falls slowly | Rises rapidly (hours) and falls rapidly |
| Best for | Monitoring chronic inflammation (TB, autoimmune diseases) | Detecting acute infections and monitoring treatment response |
| Affected by | Age, gender, anaemia, pregnancy, protein levels | Fewer confounding factors; more specific to inflammation |
| Specificity | Less specific | More specific for inflammation |
Your doctor may order both tests together to get a more complete picture of inflammation in your body.
What Should You Do Next?
- Normal ESR: No action needed regarding inflammation. Continue routine follow-up as advised.
- Mildly elevated: May not be clinically significant, especially in older adults. Your doctor will consider it alongside your symptoms.
- Moderately elevated: Further investigation is usually needed (blood cultures, CRP, chest X-ray, autoimmune markers) to identify the cause.
- Severely elevated (above 100): Indicates a serious underlying condition. Prompt medical evaluation is essential.
Important: ESR is a non-specific test. A normal ESR does not rule out disease, and an elevated ESR does not diagnose a specific condition. Your doctor uses ESR as one piece of a larger diagnostic puzzle. Never self-diagnose based on ESR alone.