Measurement of phenylalanine in routine care of phenylketonuric children

phenylalanine in routine care of phenylketonuric children. Fluorimetry, paper and column chromatography, and bacterial inhibition assay have been com-pared in the quantitation of serum or blood phenylalanine at levels ranging from 1 to over 30 mg/100 ml. Special attention was paid to levels of 2 mg or less and to those in excess of 20 mg/100 ml, since these have therapeutic implications. Bacterial inhibition assay, under routine conditions, tended to read low or not at all at 2 mg or less, and to read high above 20 mg/100 ml so that it 'failed safe ' under such condi-tions. Paper chromatography was shown to be a simple, rapid, and economic method of getting accurate results at all levels in the range examined. The accuracy with which laboratory methods, already tried and approved in research conditions, are routinely applied may vary widely in different hospitals and possibly even in different centres. This was convincingly shown in comparisons made by Wootton and King (1953), and played a part i