Evaluation of vitamin E deficiency in children with lung disease.

The clinical assessment of vitamin E status has traditionally depended upon measurement of tocopherol concentrations in plasma or serum, with 0.5 mg/dl being used as the lower limit of normal. This approach can be supplemented by measurement of tocopherol in erythrocytes or by evaluating their susceptibility to hemolysis in the presence of hydrogen peroxide. Data obtained during the last decade indicate that tocopherol concentrations in blood samples may be misleading, and that tocopherol-lipid ratios are more reliable indicators of vitamin E status. In our studies, small populations of healthy children have been evaluated, along with infants and children with a variety of chronic diseases. Of interest is the observation that premature infants susceptible to lung disease, who often require high levels of inspired oxygen, and children with cystic fibrosis who have chronic obstructive pulmonary disease are almost invariably below 0.5 mg tocopherol per deciliter plasma. A substantial number, however, show no abnormality in peroxide-induced erythrocyte hemolysis. Expression of the tocopherol data per gram of total lipid indicates that many children with "low" tocopherol concentrations per unit volume of plasma are not deficient in vitamin E, but rather are above 0.8 mg/g, the ratio of tocopherol to lipid previously reported as the lower limit of normal.