Why is my finger stick often different that the laboratory glucose test?
Is there a difference between whole blood and plasma glucose test results ?
We all put a lot of faith in our home glucose testing equipment and feel comfortable making management decisions based on the test results. However, have you ever wondered why your finger stick capillary test is often different than the venous glucose test done in a laboratory. There are a number of variables effecting your glucose test results.
The source of the blood sample ( arterial , capillary or venous ) and how the blood was processed all make a difference . Whole blood is usually removed from a vein in our arm and then put into a centrifuge and separated into plasma and red blood cells. The glucose test is then done on the plasma component of the blood. Whole blood can also be allowed to clot which separates the blood into red blood cells and serum. Your finger stick test is measuring whole blood glucose taken from capillaries in your finger and done on a machine with it's own built in error rate. The last time I checked, meters are required to have an error rate of < 20% at glucose levels of 30 to 400 mg/dl.