ESR above or below normal: causes in athletes and what to do

ESR outside the normal range is a reason not for panic but for careful analysis. In athletes this indicator can change because of anemia, a recent cold, an injury or even features of the test itself, and in rare cases signal a serious illness. The editorial team examines the most typical causes of elevated and reduced ESR and offers a sequential plan of action.

Elevated ESR: common "sports" causes

The most frequent cause of a moderately elevated ESR in an active person is a recent infection. Since fibrinogen and immunoglobulins are eliminated slowly, the ESR can remain higher than usual for several weeks after a cold or tonsillitis has already passed. The person feels healthy, but the test "has not yet caught up".

The second frequent cause is anemia. When there are fewer erythrocytes, they settle faster, and the ESR rises without inflammation. Iron deficiency is especially common among female athletes, long-distance runners, vegetarians and athletes with an energy deficit. Therefore an elevated ESR should always be assessed together with hemoglobin and ferritin.

The third is injuries and operations. Fractures, significant sprains, dental interventions, surgical operations cause an inflammatory response, and the ESR may be elevated for some time after healing.

Finally, the result is affected by excess fat mass, pregnancy and menstruation, as well as taking hormonal contraceptives. In female athletes these factors should be taken into account when comparing tests over time.

Elevated ESR: medical causes

A persistently elevated ESR, especially significantly, can indicate chronic inflammatory or autoimmune diseases: rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel disease, systemic vasculitis. In young athletes these diseases often masquerade as "overload" — pain in the lower back, heels, joints, especially in the morning or after rest.

Chronic infections — tuberculosis, osteomyelitis, endocarditis, hidden dental foci — also raise the ESR. In such cases a person usually has additional signs: a prolonged low-grade fever, night sweats, weight loss, general weakness.

A very high ESR (over 100 mm/h) almost always has a serious cause. According to a review by Brigden (1999), most often these are infections, malignant tumors (in particular multiple myeloma and lymphomas), kidney diseases and systemic inflammatory diseases. Such a result requires examination without delay.

Chronic kidney disease, hypothyroidism and conditions with an elevated level of immunoglobulins can also raise the ESR. Therefore, with an unexplained increase a doctor usually also assesses creatinine, TSH and blood protein fractions.

Low ESR: what it means

A low ESR in itself rarely has clinical significance and in most cases does not require action. However, in athletes it can be an indirect sign of an elevated hematocrit: when there are many erythrocytes in the blood, they interfere with each other's settling.

An elevated hematocrit in an athlete may be linked to dehydration, prolonged stay at altitude, smoking, sleep apnea, as well as the use of substances that stimulate erythropoiesis. Supraphysiological testosterone and anabolic steroids cause erythrocytosis, and erythropoietin and its analogs are banned by WADA and carry a risk of thrombosis. A high hematocrit increases blood viscosity, so it requires a doctor's assessment.

Other causes of low ESR are congenital changes in erythrocyte shape (sickle cell anemia, spherocytosis), very low fibrinogen, as well as some medications. Technical errors — delay of the analysis, cooling of the sample, an incorrect ratio of blood and anticoagulant — can also underestimate the result.

An important practical point: in a person with a high hematocrit a "normal" ESR can hide inflammation. Therefore, with symptoms of infection it is better to rely on CRP, which is almost independent of the number of erythrocytes.

How to make sense of a deviation

The editorial team suggests acting sequentially. First, assess the context: whether you have been ill in the last month, whether there were injuries, operations, dental treatment, competitions. If so and you feel well, it is reasonable to repeat the test in 4–6 weeks.

Next, look at the other indicators of the same test. Hemoglobin and hematocrit will show whether the change in ESR is explained by anemia or erythrocytosis. It is useful to add CRP and ferritin: a normal CRP with an elevated ESR more often indicates a "tail" after a past infection or anemia than active inflammation.

If the ESR is persistently elevated and there are symptoms — pain in the joints or back, especially at night or in the morning, low-grade fever, weight loss, night sweats — a consultation with a physician or rheumatologist is needed. One should not train "through the pain" in the hope that it is ordinary overload.

1. Assess the events of the last 4–6 weeks (infections, injuries).
2. Check hemoglobin, hematocrit, ferritin and CRP.
3. Repeat the test at the same laboratory under standard conditions.
4. With a persistent deviation or symptoms — see a doctor.

With a low ESR the main focus is hematocrit and hemoglobin. If they are elevated, a doctor will determine the cause of the erythrocytosis and assess the risk of thrombosis.

Typical interpretation errors

The first error is to perceive ESR as an "inflammation test". In reality it is affected by so many factors that without taking into account anemia, age, sex and other tests, conclusions are often wrong. A review by Sox and Liang (1986) warned several decades ago against using ESR as a screening test in people without symptoms.

The second error is to compare results of different methods. Values by the Panchenkov and Westergren methods, as well as different automatic analyzers, may differ, especially in the upper range. For monitoring it is better to use one laboratory.

The third is to expect quick normalization. ESR responds slowly, and repeating the test a few days after illness makes no sense. For assessing the current state, CRP is better suited.

The fourth is to ignore a very high ESR if "nothing hurts". Values over 100 mm/h are rarely accidental and always require explanation.

Editorial conclusions

Elevated ESR in an athlete is most often explained by a recent infection, injury or anemia, but a persistent or very high value requires a search for more serious causes.

Low ESR is usually not a problem but may point to an elevated hematocrit, which in itself requires a doctor's assessment.

ESR should be interpreted only together with hemoglobin, hematocrit, ferritin and CRP, taking into account age, sex and recent events.

We also recommend reading our materials on what the ESR test shows, on the causes of elevated C-reactive protein and on hematocrit and the risks of blood thickening in sport.

References

1. Brigden ML. Clinical utility of the erythrocyte sedimentation rate. Am Fam Physician. 1999;60(5):1443–1450.
2. Sox HC Jr, Liang MH. The erythrocyte sedimentation rate: guidelines for rational use. Ann Intern Med. 1986;104(4):515–523.
3. Harrison M. Erythrocyte sedimentation rate and C-reactive protein. Aust Prescr. 2015;38(3):93–94.
4. 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.
5. 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.
6. Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.