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Erythrocyte Sedimentation Rate (ESR)

When anticoagulated whole blood is allowed to stand, red blood cells settle out. The rate at which they fall is known as the erythrocyte sedimentation rate and is a rough measure of abnormal concentrations of acute phase proteins and immunoglobulins. This property makes ESR a sensitive, but nonspecific, indicator of tissue damage and inflammation.

Elevated ESR is an important diagnostic criterion for polymyalgia rheumatica and temporal arteritis, because these two diseases have few laboratory markers other than ESR elevation. ESR may be helpful in detecting occult disease. The most common causes of an elevated ESR in outpatients are infection, malignancy, and renal disease. The most common causes of extremely elevated ESR (>100 mm/hr) are infection, collagen vascular disease, metastatic cancer, and myeloma. ESR can be followed serially to monitor the course of a disease such as systemic lupus erythematosis or rheumatoid arthritis. ESR usually decreases within a few days after initiating corticosteroid therapy, but usually remains at a higher level than normal, even when the patient’s clinical status has dramatically improved.

ESR may be helpful in the diagnosis of coexisting iron deficiency in patients with the anemia of chronic disease. Serum iron and transferrin saturation often cannot distinguish between these two conditions. In healthy people, ferritin is a sensitive measure of tissue iron stores. A value less than 15 ng/mL usually indicates iron deficiency. However, ferritin is an acute phase reactant and levels can rise above 15 ng/mL in patients with iron deficiency and inflammation. In this situation, ESR can be used to correct ferritin levels for the degree of inflammation present. When serum ferritin is >80 ng/mL, iron deficiency is unlikely, regardless of the ESR. When ferritin falls between 15 and 80 ng/mL, the likelihood of iron deficiency can be determined from a nomogram that plots ferritin levels against ESR (Amer J Clin Pathol 1988; 90:85-87).

The acute phase proteins that affect ESR are fibrinogen, C-reactive protein, alpha-1 antitrypsin, and haptoglobin. Acute phase proteins increase with acute tissue damage and inflammation such as occurs in myocardial infarction, collagen vascular disease, malignancy and chronic infection. Elevated immunoglobulins, including monoclonal gammopathy, also increase ESR.

Other factors may also affect ESR. Red cell changes are especially prone to affect ESR. If hematocrit is reduced, red cell aggregates sediment faster. The more severe the anemia the higher the ESR. Macrocytes settle more rapidly than normal red blood cells, while microcytes settle more slowly. Sickle cells interfere with rouleaux formation and retard sedimentation.

Factors Increasing ESR

Factors Decreasing ESR

Anemia

Polycythemia

Macrocytosis

Microcytosis (Hb C)

Female gender

Sickle cells, spherocytes

Age >50 years

Anti-inflammatory medications

Obesity

Hypogammaglobulinemia

Pregnancy

Hypofibrinogenemia (DIC)

Hypercholesterolemia

High WBC count

Hyperviscosity

Sex and age may influence ESR. Women are noted to have higher ESR values than men.

Reference range using a Ves-matic 20 instrument is 0 ‑15 mm/hr in men and 0 - 20 mm/hr in women. Elderly people tend to have slightly higher ESR. Over age 50, the upper limit of normal is 20 mm/hr in men and 30 mm/hr in women.

Specimen requirement is a 5 mL lavender top (EDTA) tube of blood.

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