Erythrocyte sedimentation rate

In medicine, the erythrocyte sedimentation rate, also called sed rate or ESR, is "Measurement of rate of settling of erythrocytes in anticoagulated blood." High values may be due to high fibrinogen (Coagulation factor I) levels in the serum.

The test is nonspecific, but an elevated level is usually due to inflammation or infection. It has the great advantage of needing extremely simple equipment to perform, but more specific tests are often preferred to have more diagnostic significance. ESR can be useful, however, as a surrogate marker treating a known condition that elevates it; effectiveness of therapy can be inferred from a relative lowering of the measurement.