posted
Do you know if there is any difference in the accuracy of the Hemocue test v. hemocrit (done w/ a Hematostat)?
Would either test be affected by having drunk large volumes (in excess of a pint) of water about an hour beforehand?
And what are the relative scales for each? If I'm understanding correctly, the Hemocue uses a scale of g/dL, while the hematocrit looks at what percentage of the blood is made up of RBCs. Is that right? Is there some way to convert between the two scales? What are the ranges -- average, normal, mild anemia, severe anemia?
I went to give blood today at a different place than I usually do, and they use a different method than the place I usually go. I believe I would have qualified to give where I go normally (I've been sure to get plenty of iron from several sources in the past week+), but I was turned away by them.
This seems to indicate that water might be part of the issue w/ a Hemocue test. (They did retest with venous blood, but they used the SAME test on it!)
And this seems to indicate that the place I went has an unusually high cutoff -- 12.5, not 12.0. (Mine was 12.2.)
posted
rivka, offhand I have no idea. I don't have much experience with using different tests, just how to interpret the ones from our lab. If nobody else can help you here, I'll start digging to find out what I can.
Posts: 14017 | Registered: May 2000
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posted
Thanks. My problem is I know some of the correct terms, but not all -- sounds like you would have a related problem.
Posts: 32919 | Registered: Mar 2003
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posted
I found this description of how the hemocue works
quote:The Hemocue system uses 10 ml of blood collected into a special cuvette whose walls are lined with the dry reagents. The reagents react spontaneously with the blood sample resulting in erythrocyte membrane disintegration allowing for Hb release. Methemoglobin is formed by the conversion of iron from the ferrous to the ferric state, which combines with azide to form azide methemoglobin.14 Absorbance is read at 2 wavelengths as a means of controlling for sample turbidity. The apparatus converts the readings into Hb and displays the results digitally (g/dl).
My first impression is that mild over-hydration is no more likely to cause an error in this measurement than in a hemostat. I would be more concerned about erroneous reading from dehydration.
The hemocue is measuring hemoglobin concentrations where as a hemostat is measuring the volume of RBCs. When you suffer from iron deficiency anemia, you have both a lower number of RBC and less hemoglobin in each cell. It's possible that if you are on the border of being anemic, a measure of hemoglobin might be below the threshold before your hemotocrit drops below the threshold.
It's also noteworthy that the hemocue has to be regularly calibrated (unlike the hemostat). If the hemocue in question had not been calibrated recently it, the reading might have been off. I'd be curious to know if this center rejecting an unusual percent of donors that day.
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My problem is I know some of the correct terms, but not all -- sounds like you would have a related problem.
