1 Associate Professor of Pharmacology, University of North Carolina, Medical School, Chapel Hill, North Carolina 27514
A recent publication in your journal points out that the blood and serum levels of phenylalanine as analyzed by the method of McCaman and Robins rise as the sample ages unless the samples are kept in the frozen state. The use of refrigerated trucks in sample transportation is described as a means of dealing with the problem, which is an extremely important one in view of the many large scale screening programs for phenylketonuria now in progress. A one sentence reference is made to the use of filter paper for storage and transport of blood samples but the reader is given no clue as to what the merits of this approach are.