Methods for assessing the level of nutrition of the human subject. Estimation of vitamin B1 in urine by the thiochrome test

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Abstract
Modifications in technique have overcome the principal sources of error in this test: incomplete adsorption; interference from non-specific fluorescing substances, and other reducing substances; pigments. Special features of the new technique are: the omission of any adsorption process; regulation of the amt. of K ferricyanide added; special treatment of filter paper and reagents used; removal of interfering substances, both by preliminary washing of the urine with isobutanol and subsequent extraction of the isobutanol-thiochrome phase; direct visual comparison of fluorescence. The method is rapid and is accurate when checked against biological assays; added vit. B1 can be recovered with an error of less than 10%, and 5 ml. of urine are sufficient for a detn. The usual range of excretion for normal subjects is 50-80 I.U. daily, with a maximum of 160 and a minimum of 30. Lowered reserves of the vit, are found in pregnancy and in "conditioned deficiency" attributed to anorexia or faulty utilization. Test doses should be given to confirm a diagnosis of deficiency.

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