THE CLINICAL SIGNIFICANCE OF FREE AND ESTERIFIED VITAMIN A OF BLOOD PLASMA

Abstract

1. Various methods have been advanced for diagnosing the degree of vitamin A deficiency clinically. It was found that the method of loading with vitamin A, followed by measuring the fecal vitamin for determining the saturation of the vitamin is without value. The method of measuring the vitamin A content of the blood is therefore preferable.
2. For diagnosing vitamin A deficiency from the plasma vitamin level, the determination of the total vitamin is significant but that of the free form is more significant. The determination of the esterified form is of no significance since it remains unchanged in deficiency.
3. In some cases of nephritis, nephrosis and the diseases suggesting hepatic dysfunction the blood total vitamin A level rises, the ratio of the free/esterified showing a characteristic change. Such exception must be taken into consideration.
4. The plasma vitamin A levels in 49 apparently healthy subjects were determined. The total vitamin A was 140.3±35.9, the free form 116.6±35.2 and the esterified form 23.7±11.0 I. U./100ml, hardly dependent of age; 82.6per cent of the total vitamin A is in the free form and 17.4 per cent in the esterified form.
5. Determination of the plasma vitamin A level, below which can be considered a deficiency, is a difficult problem and must await further investigation. However, when the total vitamin A level drops below 90 I. U./100ml and the free form below 70 I. U. 100ml, there is clearly a vitamin A deficiency, supplementation of vitamin A being urgently required.