Oral Glucose Tolerance Test

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amberdagp
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Oral Glucose Tolerance Test

Post by amberdagp » Sun Mar 22, 2009 9:16 pm

I cant really understand this, can someone please help me, i have tried to think what the answer may be but I am not sure.

In an Oral Glucose Tolerance Test, a patients blood (plasma) sample had to be diluted with water, whilst other samples were not.

Firstly, does this dilution mean the amount of glucose will have to be calculated to which it should have been before this patient's sample was diluted?

Secondly, why was the sample diluted with distilled?
As the blood samples were centrifuged, the blood cells were taken out and what was left was the plasma. Does this mean this patient had some blood cells left over that the sample had to be diluted or is there another reason?

Many thanks!!!!
Kind regards

blcr11
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Re: Oral Glucose Tolerance Test

Post by blcr11 » Mon Mar 23, 2009 3:13 am

Plasma is the aqueous phase of blood after the cells have been spun out. There shouldn't be any cells left, if the samples have been processed correctly. In diabetics, especially following ingestion of such a large amount of glucose administered by the OGTT, plasma glucose levels are expected to be very high; often exceeding the linear range of the glucose assay. So you dilute the samples to reduce the amount of glucose in the assay to get better accuracy. You then have to adjust the assay value by the dilution factor to calculate the glucose level in the original, undiluted plasma sample. Say you diluted the sample by a factor of 10 (1 part plasma + 9 parts distilled water) and determine the glucose concentration in the diluted plasma to be 70 mg/dl. The concentration in the undiluted plasma was 10 x 70 or 700 mg/dl. Non-diabetics don't have such high levels of plasma glucose, so their samples don't need to be diluted in order to be measured accurately.

amberdagp
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Post by amberdagp » Mon Mar 23, 2009 6:10 pm

Excellent answer:) thank you very much!

amberdagp
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Post by amberdagp » Mon Mar 23, 2009 9:25 pm

Can anyone recommend any good books in reference to the Oral Glucose Tolerance Test?

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