A manual fluorometric paper disc method for detecting phenylketonuria.

THE MICROBIOLOGIC PROCEDURE of Guthrie and Susi (1) is probably the most widely used screening technic for detecting phenylketonuria. The method of McCaman and Robins (2) and its modifications by Wong et al. (3) and Hsia et at. (4), as well as that of La Du and Michael (5) are the chemical procedures generally used as confirmatory tests. Hill et at. (6) have adapted the McCaman procedure to the AutoAnalyzer for determining phenylalanine in blood and in filter paper discs saturated with blood. More recently Bourdillon and Vanderlinde (7), using autoclaved blood discs, increased the sensitivity of the Hill procedure. Autoclaving the blood filter paper discs coagulated the proteins and obviated the need for the dialyzer required in the automated procedure. After autoclaving, the phenylalanine may be eluted with water while the denatured proteins remain bound to the filter paper discs. The method described in this paper will enable other workers to perform the test for phenylalanine on the material eluted from the blood disc without the use of automated equipment. Hill showed that blood discs stored at room conditions are stable for at least 27 days. Our own experiments showed blood discs to be stable for at least 3 months if stored in the dark at 5#{176} in a desiccator over silica gel. However, less exacting conditions may be adequate for storage of the discs.