● Using the wrong volume of blood to anticoagulant.
● Blood not sufficiently mixed with anticoagulant.
● Clots in the blood. Even the smallest fibrin clot in the sample will invalidate the test result.
● Air bubbles at the top of the column.
● Testing blood samples at the hottest time of the day, or leaving tests in direct sunlight. Temperatures over 25°C increase sedimentation.
● Using a pipette which is not clean or not dry.
● Pipette not positioned vertically. Even slight variations from the upright increase sedimentation.
● Not checking whether the ESR stand is level on the bench.
● Placing an ESR stand on the same bench as a centrifuge where vibration will interfere with sedimentation.
● Measuring the ESR when a patient is dehydrated.
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