ESR Blood Test: What Your Sedimentation Rate Means and What Comes Next

What is the ESR test and how is it measured?

ESR stands for erythrocyte sedimentation rate. The principle is straightforward: a sample of your blood is placed in a tall narrow glass tube and left upright for one hour. During that hour, the red blood cells settle toward the bottom under gravity, and the distance they have fallen in millimetres is the result. The faster they fall, the higher the number.

The internationally accepted reference method is the Westergren method, which is used in most laboratories across the region. A raised ESR happens because certain proteins produced by the liver during inflammation, particularly fibrinogen and immunoglobulins, cause the red blood cells to clump together into stacks called rouleaux, which fall faster than individual cells.

The ESR has been in clinical use for over a hundred years, making it one of the oldest inflammation tests in medicine. Brigden, writing in the American Family Physician in 1999, noted that ESR has remained in everyday use despite its age precisely because it is inexpensive and available in every laboratory. Its low cost and simplicity have kept it in everyday use even as newer, more specific markers have been developed.

In the Arab world specifically, ESR is frequently requested because the diseases most prevalent in the region, including brucellosis, tuberculosis and rheumatoid arthritis, all produce a raised ESR and require long-term monitoring, which is something ESR handles better than almost any other inflammation test.

What is a normal ESR?

The normal range for ESR depends on age and sex, which is one of the most common sources of confusion when reading a result. ESR rises naturally with age even in healthy individuals, so what is normal for a young adult is different from what is normal for an older person.

A widely used approximation for the upper limit of normal is: for men, divide their age by two; for women, add ten to their age and divide by two. A 50-year-old man therefore has an upper normal of about 25 mm/h, while a 50-year-old woman's upper normal is about 30 mm/h. This is an approximation, and the reference range printed on your report is the more precise guide.

ESR also rises normally during pregnancy, during menstruation, and in people who are obese. Your doctor takes all these factors into account before interpreting the result. A borderline result, one that sits five to ten points above the reference upper limit in a person who feels well, does not usually require urgent investigation and may be managed with a repeat test in a few weeks.

Where does your ESR sit?

Once you know the normal range for your age and sex, you can compare your result. What matters is not just whether the result is above normal, but by how much. A result mildly above the reference range by five or ten points is a very different clinical situation from a result of 80 or 100 mm/h.

A dramatically elevated ESR above 100 mm/h is almost always caused by something that warrants investigation. The most common causes at this level are severe rheumatic disease, malignancy and serious infection including tuberculosis. A result this high without a known cause should prompt the doctor to investigate without delay.

A borderline result, meaning a value just above the upper limit of normal, in a person who feels well and has no other concerning symptoms, may need only a repeat test in four to six weeks, combined with a CRP to see whether any active inflammation is detectable by a faster marker.

Common causes of a raised ESR in this region

Tuberculosis is the single most important cause to exclude when ESR is raised in this part of the world. The WHO Global Tuberculosis Report 2023 notes that several countries in the region continue to carry a moderate to significant TB burden. Pulmonary tuberculosis produces a persistently raised ESR, typically accompanied by a chronic cough lasting more than three weeks, night sweats, weight loss and a low-grade fever. These symptoms alongside a raised ESR make TB investigation a priority before moving to other causes.

Brucellosis, known as Malta fever or undulant fever, is a bacterial infection common across the region, particularly in rural areas where cattle and sheep are kept and unpasteurised dairy products are consumed. Fresh local cheese and raw milk are the most frequent sources of infection in this setting. Brucellosis raises the ESR significantly and presents with a distinctive swinging fever, joint pains and profound fatigue. It can closely resemble tuberculosis in its early presentation.

Rheumatic diseases including rheumatoid arthritis, lupus and giant-cell arteritis produce a persistently raised ESR. Schmidt and Warrington, writing in Drugs and Aging in 2011, highlighted that a markedly elevated ESR is one of the key diagnostic criteria for giant-cell arteritis, which typically affects adults over 60 and can cause permanent vision loss if untreated. Any older adult with a new severe headache and ESR above 50 mm/h should be assessed urgently.

ESR versus CRP: what is the difference and when is each used?

Doctors sometimes order ESR and CRP together, which is not redundant. Each test has a different time profile that makes it useful in different circumstances.

CRP rises fast, starting within six hours of the start of inflammation, and it falls quickly, within days of the cause resolving. ESR is much slower: it takes days to rise and can remain elevated for weeks even after the infection has cleared. This makes CRP better for diagnosing acute infections and monitoring short-term treatment response, while ESR is more useful in chronic inflammatory diseases and long-term monitoring.

A study by Osei-Bimpong and colleagues published in Hematology in 2007 concluded that CRP is more sensitive and specific for diagnosing acute infection than ESR, but that ESR remains useful in chronic disease monitoring and in situations where CRP is normal despite ongoing low-level inflammation.

When is a raised ESR not a sign of serious disease?

Not every elevated ESR signals a dangerous condition. It rises mildly in many benign situations: pregnancy, obesity, anaemia of any cause, older age and certain medications such as corticosteroids. It also remains elevated for weeks after a simple viral infection has fully resolved, which is a normal consequence of the test's slow time course.

Some people have a mildly elevated ESR chronically without any identifiable cause, which is described as unexplained elevation. If a thorough assessment finds nothing, the doctor typically monitors the situation periodically rather than investigating further. A reassuring sign in this situation is a normal CRP: a persistently normal CRP alongside a mildly raised ESR in a person who feels well suggests that no major active inflammation is present.

ESR is most useful as a pointer that something may be worth investigating, not as a verdict in itself. The clinical picture, symptoms and other tests always carry more weight than the number alone.

What happens after a raised ESR is found?

When a doctor finds a raised ESR, they connect it to the full clinical picture: what are your symptoms, how long have they lasted, what is your medical and family history, have you lost weight, do you have a fever, have you been exposed to unpasteurised food or animals, and are you taking any medication that affects the result? These questions direct the investigation far more than the number alone.

Additional tests typically requested alongside a raised ESR include CRP for comparison, a full blood count to look for anaemia and signs of infection, liver and kidney function tests, and specific tests for tuberculosis such as an IGRA test or sputum microscopy if TB is suspected. A chest X-ray is often requested at the same time.

A mildly raised ESR without symptoms in an otherwise healthy young adult may be managed with a repeat test in one to two months. A value above 50 mm/h with accompanying symptoms warrants faster investigation.

How much does the ESR test cost and where is it available?

ESR is one of the least expensive tests available in the region. In Syria, Iraq, Egypt, Jordan and Saudi Arabia it is performed at virtually every private and public laboratory at a low fixed cost, and results are typically available within hours on the same day. The test requires no specialist equipment, which means it is accessible even in small district hospitals and rural clinics.

Because of its simplicity it is often requested as part of a standard panel alongside CBC, CRP and basic chemistry tests. If your budget is limited and your doctor has requested both ESR and CRP, know that both are inexpensive by regional standards, and running them together provides information that neither test alone can supply.

For long-term monitoring in conditions such as rheumatoid arthritis or during TB treatment, ESR is usually repeated every one to three months. Keeping copies of your past results is important because your doctor needs to see the trend over time rather than a single isolated number. A falling ESR is usually the clearest sign that treatment is working.

Sources

• Brigden ML: Clinical utility of the erythrocyte sedimentation rate, American family physician, 1999
• Osei-Bimpong A, Meek JH, Lewis SM et al: ESR or CRP? A comparison of their clinical utility, Hematology (Amsterdam, Netherlands), 2007
• Schmidt J, Warrington KJ: Polymyalgia rheumatica and giant cell arteritis in older patients: diagnosis and pharmacological management, Drugs and aging, 2011
• Hameed MA et al: ESR and CRP in connective tissue diseases, Damascus University Medical Journal, 2017
• WHO: Global tuberculosis report 2023, World Health Organization
• Pepys MB, Hirschfield GM: C-reactive protein: a critical update, Journal of Clinical Investigation, 2003