Always In Control (AIc)
A1c is one of the most important tests you can do so we have dedicated this site to everything
you need to know about it including a Blog and a Wiki where you can help us post information on
Diabetes.
you need to know about it including a Blog and a Wiki where you can help us post information on
Diabetes.
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Glucose Molecue
Historically, blood glucose values were given in terms
of whole blood, but most laboratories now measure
the serum glucose levels. Because RBC
(erythrocytes) have a higher concentration of protein
(i.e. hemoglobin) than serum, serum has a higher
water content and consequently more dissolved
glucose than does whole blood. To convert from
whole-blood glucose, multiply the value by 1.15 to give
the serum/plasma level.
Collection of blood in clot (red-top) tubes for serum
chemistry analysis permits the metabolism of glucose
in the sample by blood cells until separated by
centrifugation. Very high WBC counts can lead to
excessive glycolysis in the sample with substantial
reduction of glucose level. Ambient temperature at
which the blood sample is kept prior to centrifugation
and separation of Plasma/Serum also affects glucose
levels. At refrigerator temperatures, glucose remains
relatively stable for several hours in the blood sample.
At room temperature (25°C), a loss of 1 to 2% of
glucose per hour should be expected.
of whole blood, but most laboratories now measure
the serum glucose levels. Because RBC
(erythrocytes) have a higher concentration of protein
(i.e. hemoglobin) than serum, serum has a higher
water content and consequently more dissolved
glucose than does whole blood. To convert from
whole-blood glucose, multiply the value by 1.15 to give
the serum/plasma level.
Collection of blood in clot (red-top) tubes for serum
chemistry analysis permits the metabolism of glucose
in the sample by blood cells until separated by
centrifugation. Very high WBC counts can lead to
excessive glycolysis in the sample with substantial
reduction of glucose level. Ambient temperature at
which the blood sample is kept prior to centrifugation
and separation of Plasma/Serum also affects glucose
levels. At refrigerator temperatures, glucose remains
relatively stable for several hours in the blood sample.
At room temperature (25°C), a loss of 1 to 2% of
glucose per hour should be expected.
The loss of glucose levels in aforementioned conditions can be prevented by using Fluoride top (gray-top) as
the anticoagulant of choice upon blood collection, as Fluoride inhibits glycolysis. However, this should only be
used when blood will be transported from one hospital laboratory to another for glucose measurement.
Red-top serum separator tubes also preserve glucose in samples once they have been centrifugated to
isolate the serum from cells, this tube would be the most efficient. Particular care should be given to drawing
blood samples from the arm opposite the one in which an intravenous line is inserted, to prevent
contamination of the sample with intravenous fluids (IV). Alternatively, blood can be drawn from the same arm
with an IV line after the IV was turned off for at least 5 minutes and the arm is elevated to drain the infused
fluids away from the vein. As little as 10% contamination with 5% dextrose (D5W) will elevate glucose in a
sample by 500mg/dl or more. Arterial, capillary and venous blood have comparable glucose levels in a fasting
individual, whereas after meals venous levels are lower than capillary or arterial blood.
the anticoagulant of choice upon blood collection, as Fluoride inhibits glycolysis. However, this should only be
used when blood will be transported from one hospital laboratory to another for glucose measurement.
Red-top serum separator tubes also preserve glucose in samples once they have been centrifugated to
isolate the serum from cells, this tube would be the most efficient. Particular care should be given to drawing
blood samples from the arm opposite the one in which an intravenous line is inserted, to prevent
contamination of the sample with intravenous fluids (IV). Alternatively, blood can be drawn from the same arm
with an IV line after the IV was turned off for at least 5 minutes and the arm is elevated to drain the infused
fluids away from the vein. As little as 10% contamination with 5% dextrose (D5W) will elevate glucose in a
sample by 500mg/dl or more. Arterial, capillary and venous blood have comparable glucose levels in a fasting
individual, whereas after meals venous levels are lower than capillary or arterial blood.
For more information:
http://en.wikipedia.org/wiki/Blood_sugar
http://en.wikipedia.org/wiki/Blood_sugar