ESR

Also seen on reports as: Sed Rate, Sedimentation Rate, Westergren ESR

What is ESR?

ESR (Erythrocyte Sedimentation Rate) is one of the oldest blood tests in medicine. It measures how quickly red blood cells (erythrocytes) settle to the bottom of a thin vertical tube in one hour. The principle is simple — when there is inflammation in the body, certain proteins (mainly fibrinogen) make red cells stick together and settle faster, so the ESR number rises.

ESR is a non-specific marker — it tells the doctor that something is generating inflammation somewhere, but not what or where. Many different conditions raise ESR — infections, autoimmune disease, certain cancers, pregnancy, anaemia itself, and ageing. Many people with completely normal ESR also have inflammation that just isn't reflected on this particular test.

The test uses a tall thin tube of blood mixed with anticoagulant; the result is read after exactly one hour. NABL-accredited Indian labs typically report ESR using the Westergren method, in millimetres per hour (mm/hr).

Why doctors order it

ESR is one of the most ordered tests in Indian outpatient practice. It is part of many routine panels, and doctors order it when symptoms are vague — persistent fever, unexplained tiredness, joint pain, persistent low-grade illness — to help decide whether further work-up is needed.

It is also routinely used in monitoring conditions known to involve inflammation — rheumatoid arthritis, lupus, vasculitis, polymyalgia rheumatica, temporal arteritis, inflammatory bowel disease. In Indian practice, ESR is often ordered in suspected tuberculosis (where it tends to be raised) and in following up TB treatment response.

ESR is sometimes used during work-up for unexplained anaemia, certain blood cancers (multiple myeloma classically raises ESR substantially), and as one input — alongside symptoms and other tests — in conditions where inflammation is part of the picture. It is, however, less specific than newer markers (CRP, hs-CRP) and is increasingly used alongside them rather than alone.

What the result means

A raised ESR is a signal that something is generating inflammation somewhere — but it does not say what. Mild elevations (just above the upper limit, often age-related) are common and frequently non-specific. Moderate elevations (40–80 mm/hr) usually warrant looking for an underlying cause — infection, autoimmune disease, chronic illness. Very high elevations (>100 mm/hr) have a much narrower list of likely causes — significant infection (tuberculosis classically in Indian practice), some malignancies (multiple myeloma in particular), severe autoimmune disease, or major tissue injury.

A normal ESR does not rule out inflammation. Some active inflammatory conditions can have normal ESR — particularly in their early or mild forms. Conversely, several non-inflammatory conditions raise ESR — pregnancy (raised throughout, particularly in the third trimester), age (ESR rises with age in both sexes), and anaemia of any cause (low red cell numbers shift the test).

Many modern guidelines recommend pairing ESR with CRP when assessing inflammation. ESR responds slowly (rises over days, falls over days to weeks) while CRP responds within hours. They give complementary information. hs-CRP, used for cardiovascular risk assessment, is a different test from regular CRP — see the hs-CRP page.

Common factors that affect the result

Age is the most under-recognised factor — ESR rises with age in both sexes. The age-adjusted upper limits (Miller's formula: age ÷ 2 for men, (age + 10) ÷ 2 for women) handle this in older patients. A mildly raised ESR in an 80-year-old is often within the age-adjusted normal range.

Anaemia raises ESR by changing red-cell behaviour in the tube. Significant iron-deficiency or chronic-disease anaemia can give a raised ESR without any new inflammation — particularly relevant in India where anaemia is widespread. Pregnancy raises ESR throughout, and the increase is normal. Oral contraceptives can mildly raise it too.

Several conditions lower ESR — polycythaemia (high red cell mass), sickle cell disease, some clotting disorders, and very high white cell counts. These are uncommon as causes of unexpectedly low ESR; most low ESR values are not clinically important. Sample handling matters — tubes that have sat too long, were not properly anticoagulated, or were measured outside the standard 1-hour window can give incorrect results.

When to talk to your doctor

• Your ESR is well above the age-adjusted upper limit, particularly with symptoms — persistent fever, unexplained weight loss, joint pain, persistent fatigue.
• Your ESR is above 100 mm/hr — this narrows the list of likely causes and usually triggers focused investigation (TB, malignancy, severe autoimmune disease).
• You have a known autoimmune condition (rheumatoid arthritis, lupus, etc.) and your ESR is rising on serial tests — this often signals a flare.
• You are being followed for tuberculosis treatment and your ESR is being tracked alongside other markers of response.
• Your ESR is raised but you feel fine and have no symptoms — usually rechecked rather than aggressively investigated, particularly in older adults where age-adjusted ranges may already cover it.

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