What are limits on ESR for diagnoses?
Q What are the limitations on using ESR as a marker for undiagnosed/active illness?
A The erythrocyte sedimentation rate (ESR) measures the distance that red cells have fallen after one hour in a vertical column of anticoagulated blood under the influence of gravity. It relates to the ability of the red cells to form rouleaux, which in turn is related to levels of fibrinogen, acute phase proteins and immunoglobulin.
This is the basis on which the test is widely used to detect and monitor disease. The ESR is increased in conditions associated with an acute phase response such as infection, inflammatory or neoplastic diseases.
Physiological increases in fibrinogen, such as during pregnancy, also raises the ESR, while hypofibrinogenaemia or cardiac failure lower it. The ESR is also influenced by cellular factors; anaemia increases the ability to form rouleaux and elevates the ESR as does macrocytosis.
Conversely, polycythaemia and small or irregularly shaped cells for example iron deficiency or sickle cells produce an artefactual decrease of the ESR. Normal values are higher for women than men and rise with age; in the elderly there is a wide overlap between health and disease.
The ESR is particularly useful in monitoring chronic inflammatory diseases so it is valuable for diagnosing and monitoring polymyalgia rheumatica or temporal arteritis and in assessing response of these conditions, as well as rheumatoid arthritis, to treatment.
The low sensitivity and specificity means the ESR has limited value as a screening tool, particularly in elderly and asymptomatic patients.
Kate Ryan is consultant haematologist at
Manchester Royal Infirmary