ESR: What the Test Shows and Why It Matters for an Athlete

The erythrocyte sedimentation rate is one of the oldest laboratory tests, which is still part of the complete blood count in many clinics. It is cheap and simple, but at the same time nonspecific and slow. The editorial team explains what ESR physically measures, why the result depends on such a number of factors and what benefit this indicator can give an athlete.

What ESR is and how it is measured

ESR is the distance in millimeters by which erythrocytes descend in a column of still blood mixed with an anticoagulant over one hour. Above the settled cells a transparent layer of plasma forms, and its height is what is measured. The result is expressed in millimeters per hour (mm/h).

The method was proposed at the beginning of the 20th century by the Swedish physician Robin Fåhræus and his colleague Alf Westergren. It is precisely the Westergren method that the International Council for Standardization in Haematology (ICSH) still considers the reference (Jou et al., 2011). In the post-Soviet countries the Panchenkov method with capillaries of a different length has also been historically common; the results of the two methods do not always coincide, especially at high values.

Modern laboratories often use automated analyzers that measure erythrocyte aggregation over a shorter time and recalculate the result into a “Westergren equivalent.” Such methods must be validated against the reference one, so when comparing results over time it is advisable to have the test done in a single laboratory.

Despite its simplicity, ESR does not measure inflammation directly. It is an indirect indicator that reflects changes in the composition of the plasma and the properties of the erythrocytes themselves.

What the result depends on

Erythrocytes have a negative surface charge and normally repel one another, so they settle slowly. When the amount of large proteins in the plasma increases — primarily fibrinogen, and also immunoglobulins — the charge is neutralized, the erythrocytes stick together into “rouleaux” and settle faster.

Fibrinogen is an acute-phase protein, so in inflammation ESR rises. However, the result is also affected by the number of erythrocytes: in anemia there are fewer of them, they settle faster, and ESR rises without any inflammation. Conversely, with an increased hematocrit (polycythemia) ESR decreases.

The shape of the erythrocytes also matters. Altered cells (for example, in sickle cell anemia) form aggregates poorly, and ESR may be atypically low even in inflammation. Technical factors — a tilt of the tube, temperature, a delay in the analysis of more than a few hours — also change the result (Brigden, 1999).

It is precisely because of such a number of factors that ESR is called a “nonspecific” test: an elevated value says that something has changed in the blood, but does not explain what exactly.

Norms and the influence of age and sex

The upper limit of normal ESR depends on age and sex. In women the values are on average higher, and with age ESR gradually rises in both sexes. Approximately, for young adult men it does not exceed 15–20 mm/h, for women — 20–25 mm/h, but the exact limits must be checked on the laboratory’s form.

For a practical calculation of the upper limit of normal, a simple rule proposed by Miller and colleagues (1983) is often used: for men — the age in years divided by 2; for women — the age plus 10, divided by 2. For example, for a 40-year-old man the upper limit will be about 20 mm/h, for a woman of the same age — about 25 mm/h.

These limits are empirical and do not take into account anemia, pregnancy or obesity. So a slight exceedance of the “norm” without symptoms is not yet a diagnosis, and a normal ESR does not rule out disease.

For athletes it is important that endurance training increases plasma volume more strongly than erythrocyte mass (“sports pseudoanemia”). This may slightly change hematological indicators, so it is best to compare your own results with previous ones obtained under similar conditions.

ESR and CRP: what the difference is

ESR and C-reactive protein are often ordered together, but they reflect different processes. CRP is a specific protein whose synthesis rises within a few hours of the onset of inflammation and quickly falls after it is resolved. ESR depends mainly on fibrinogen and immunoglobulins, which accumulate and are eliminated much more slowly.

Because of this, ESR begins to rise a day or two after the onset of inflammation and may remain elevated for weeks after recovery. In practice this means: CRP better reflects “what is happening now,” and ESR — “what has been happening recently” (Harrison, 2015).

In most acute situations CRP is considered a better marker than ESR thanks to its specificity and speed. Still, ESR retains value in certain diseases — giant cell arteritis, polymyalgia rheumatica, multiple myeloma, the monitoring of some autoimmune diseases (Bray et al., 2016).

• CRP:fast, more specific for inflammation, little affected by anemia.
• ESR:slow, depends on many factors, reflects long-term changes.
• Together:a discrepancy between them can itself be a diagnostic clue for the doctor.

Significance for the athlete

For a healthy athlete ESR is most often part of a routine complete blood count during medical examinations. A normal result is additional, though not absolute, evidence of the absence of chronic inflammation.

A moderate rise in ESR in an athlete without symptoms is more often connected with a recent infection, injury, anemia (in particular iron-deficiency anemia, which not infrequently occurs in female athletes and runners) or technical features of the analysis. So ESR should be assessed together with hemoglobin, ferritin and CRP.

ESR is useful in prolonged pain in the back, joints, Achilles tendon or heel, when a “sports” injury may turn out to be a manifestation of an inflammatory disease. A persistently elevated ESR in such a situation is an argument in favor of consulting a rheumatologist.

For assessing recovery after training or diagnosing overtraining, ESR is not suitable: it is too slow and nonspecific. Conclusions about readiness for loads are made on the basis of well-being, performance and a set of indicators.

To obtain comparable results, blood is given in the morning, at rest, without intense training the day before and outside of acute illness.

Editorial conclusions

ESR is a simple but nonspecific test that reflects changes in plasma proteins and the properties of erythrocytes rather than inflammation directly.

The norm depends on age and sex, and the result is affected by anemia, pregnancy, obesity and technical factors. Miller’s rule helps to roughly estimate the upper limit.

CRP shows current inflammation faster and more accurately, whereas ESR changes slowly and retains value in certain rheumatological and hematological conditions.

We also recommend reading our materials on the causes of elevated and reduced ESR in athletes, on C-reactive protein and on ferritin and anemia in sport.

References

1. Jou JM, Lewis SM, Briggs C, et al. ICSH review of the measurement of the erythrocyte sedimentation rate. Int J Lab Hematol. 2011;33(2):125–132.
2. Brigden ML. Clinical utility of the erythrocyte sedimentation rate. Am Fam Physician. 1999;60(5):1443–1450.
3. Miller A, Green M, Robinson D. Simple rule for calculating normal erythrocyte sedimentation rate. Br Med J (Clin Res Ed). 1983;286(6361):266.
4. Harrison M. Erythrocyte sedimentation rate and C-reactive protein. Aust Prescr. 2015;38(3):93–94.
5. Bray C, Bell LN, Liang H, et al. Erythrocyte sedimentation rate and C-reactive protein measurements and their relevance in clinical medicine. WMJ. 2016;115(6):317–321.
6. Mairbäurl H. Red blood cells in sports: effects of exercise and training on oxygen supply by red blood cells. Front Physiol. 2013;4:332.