Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1301 page)

   Malabsorption disorders, such as biliary atresia, cirrhosis, CF, chronic pancreatitis, pancreatic carcinoma, and chronic cholestasis

   Limitations

   As previously stated, serum vitamin E levels are strongly influenced by concentration of serum lipids and do not accurately reflect tissue vitamin levels. Therefore, effective vitamin E levels are calculated as the following ratio:

   Effective serum vitamin E level = alpha-tocopherol/(cholesterol + triglycerides)

   A normal ratio is >0.8 mg alpha-tocopherol/gram total lipids.

   For patients with normal levels of serum lipids, serum alpha-tocopherol levels provide an adequate estimate of vitamin E sufficiency. Alphatocopherol levels of <0.5 mg/dL (5 μg/mL) are considered deficient.

   Drugs that may increase vitamin E levels include anticonvulsants (in women).

   Drugs that may decrease vitamin E levels include anticonvulsants (in men).

   Exposure of the specimen to light decreases vitamin E levels, resulting in a falsely low result.

   Platelet tocopherol is suggested to be a better measure of vitamin E nutritional status than plasma tocopherol because it is more sensitive to vitamin E intake and is not dependent on circulating lipid levels.

VON
WILLEBRAND DISEASE (VWD) ASSAYS
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   Definition

   VWD is a bleeding disorder manifested by mucocutaneous bleeding.

   Use