Erythrocyte sedimentation rate: Principle, procedure


Blood collected into an anticoagulant is placed in a long graduated tube held in a vertical position. The erythrocyte settles to the bottom, leaving a layer of plasma above. The height of the column of plasma after 1 hour indicates the sedimentation rates of the erythrocytes.


  • Trisodium citrate 3.8% solution
  1. Dissolve 32g of Trisodium citrate in 1l of distilled water
  2. Keep the solution at 4 celsius
  • Fresh blood/EDTA anticoagulants blood
  • Westergren ESR tubes, internal diameter 2.5mm,graduated from 0 to 200mm
  • ESR racks
  • Rubber bulbs
  • Test tubes
  • Timer

Westergren tube method

  • Pipette 0.4ml of Trisodium citrate solution into a test tube
  • Add 1.6ml of blood into the same tube
  • Draw citrated blood into the Westergren tube(using a rubber bulb)up to the 0 mark
  • Place the tube in the Westergren stand. Making sure that the tube is completely upright
  • Leave on a bench for 1 hour
  • Then note the high of the column of the plasma in mm graduation starting from the 0mm mark at the top of the tube
  • Express the result as mm/1 hour

Reference ranges

  • Men up to 10mm/hour
  • Women up to 15mm/hour
  • Elderly up to 30mm/hour
  • pregnancy – (first half – up to 48mm/hour), (Second half – up to 70mm/hour)

Sources of Errors

  • Using of wrong volume of blood to anticoagulant
  • Clots in the blood
  • Air bubbles in the tube
  • Leaving mounted test tubes in direct sunlight
  • Non-vertical tubes
  • The vibration of the ESR tube
  • Using a tube which is not dry or not clean
  • High temperature
  • Incorrect reading meniscus



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