November 10, 2000
Blood Tests and Insulin Injections
Question from Carmel, California, USA:
A recent article in a national diabetes magazine stated that for hemoglobin A1c lab test results to be accurate, the sample must be put into a centrifuge within 30 minutes. I asked our local lab about this, and they stated that their protocol specified within four hours. If 30 minutes is optimal, and the reading would have been 7.0%, what would the readings show (using the same sample) at one hour, two hours, etc.? This is important to know because doctors use this as one measure of recommending certain treatments.
Answer:
I think that there has been a misunderstanding here. When blood is taken for glucose assay in a clinical laboratory, the red cells are normally spun off as soon as possible, and glucose is then measured in the serum. Nowadays, hemoglobin A1c is measured, whether in a clinical laboratory or in a doctor’s office, on a very small needle stick amount of whole blood. Even with the older chromatographic assays, whole blood was also employed.
DOB
