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Old 10-22-2012
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Default Huge doubt on thalasemias

Good afternoon guys hope you are having a good day, while i was reviewing the rbc chapter on goljan rr i read that in thalassemia you have a decreased hematocrit and an increased rbc count, i dont get it how can your rbc count be increased and your hematocrit decreased if hematocrit is the percentage of rbc that conform blood's volume?
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Old 10-22-2012
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Default Its about the Hemoglobin

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Originally Posted by OVRPS View Post
Good afternoon guys hope you are having a good day, while i was reviewing the rbc chapter on goljan rr i read that in thalassemia you have a decreased hematocrit and an increased rbc count, i dont get it how can your rbc count be increased and your hematocrit decreased if hematocrit is the percentage of rbc that conform blood's volume?

If you recall HCT actually is determined by Hb values (HCT = 3xHgb). In Thalassemia your body is not properly producing Hgb and as a result keeps spitting out RBC's leading to a high RBC count but the Hgb is still a problem in each one so even though you have a high RBC you can have a low HCT though it does seem counterintutive (if I recall this is the only place they are ever seen opposite one another)
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Old 10-22-2012
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Originally Posted by freebielady View Post
If you recall HCT actually is determined by Hb values (HCT = 3xHgb). In Thalassemia your body is not properly producing Hgb and as a result keeps spitting out RBC's leading to a high RBC count but the Hgb is still a problem in each one so even though you have a high RBC you can have a low HCT though it does seem counterintutive (if I recall this is the only place they are ever seen opposite one another)
Oooh so hematocrit is not determined by rbc count and therefore percentage of rbc in blood? Or do you mean that there are many rbc but their volume isn't that much because of the defficient globin chains?
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Old 10-22-2012
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Default Rule of threes

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Originally Posted by OVRPS View Post
Oooh so hematocrit is not determined by rbc count and therefore percentage of rbc in blood? Or do you mean that there are many rbc but their volume isn't that much because of the defficient globin chains?
Usually values follow the "rule of threes" RBC x 3 = Hb; Hb x3=Hct and HCT is determined by the amount of RBC. But not here.
In thallasemias the RBC production will be "normal" when looking at numbers (or it will be low). However the HB levels (and therefore HCT) are decreased at a much lower rate. So like you said the RBC will be very hypochromic since they do not have the right amount of Hb in them. RBC count can differ depending on the stage of thalassemia however, and you can have all values decresed but the HCT will still be lower than what you expect it to be based RBC count alone.
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