The ESR (Erythrocyte sedimentation rate) is an old fashioned test and non-specific marker of inflammation.
It is a measure (in mm/hr) of the rate at which red blood cells in a sample of anticoagulated blood (in EDTA) fall when blood is placed in an upright capillary tube.
Slightly higher in women than men and rises by 5-10mm/hr throughout life – ie the formulae using age/2 for men or (age+10)/2 for women to estimate acceptable ESRs over estimate the rise with age.
Affected by anything that increases plasma proteins – fibrinogen (cancer, inflammation), immunoglobulins (myeloma, inflammatory conditions, chronic infections, HIV), coagulation factors (pregnancy) or alters red cell count – polycythaemia or anaemia.
Uses of ESR :
- As a screening test for Temporal Arteritis or Polymyalgia Rheumatica in the context of a suggestive history.
ESR is not useful in:
- General screening for infection.
- Screening for Myeloma – ESR can be normal in 25% of myeloma.
- General screening of the unwell – it does not distinguish between cancer versus infection versus inflammation.
- General workup of a patient with a suspected rheumatological condition – consider specific tests.
- Investigating patients with anaemia, when the anaemia itself will lead to a rise in the ESR