Application of a new test for vitamin E deficiency to cystic fibrosis.

Cystic fibrosis patients with pancreatic insufficiency are at risk for the development of vitamin E deficiency. We report here the outcome of screening 13 cystic fibrosis patients with conventional descriptive measures of vitamin E status and a new functional test. The results were compared with those from age appropriate controls. Nine patients were found to be vitamin E sufficient based upon normal plasma vitamin E levels, the ratio of plasma vitamin E to total plasma lipids, and normal levels of in vitro erythrocyte malondialdehyde formation, the new functional measure of vitamin E status. Four patients considered vitamin E deficient, based upon low plasma vitamin E levels and plasma vitamin E to total plasma lipid ratios, demonstrated increased erythrocyte malondialdehyde formation in vitro when compared to age-matched controls. Since limited reference data in children are available to define normal plasma vitamin E levels and plasma vitamin E to total plasma lipid ratios, we suggest that for cystic fibrosis patients the functional in vitro malondialdehyde formation test may be a better measure of vitamin E status than static plasma levels.