Estimation of galactose-1-phosphate in blood spotted on filter paper.

A method is described for the enzymic estimation of galactose-1-phosphate (Gal-1-P) in blood which has been applied to filter paper and allowed to dry. The successful clinical management of patients with galactosemia depends upon exclusion of galactose from their diet. Earlier studies demonstrated that red cell Gal-1-P is a sensitive indicator of exposure of such patients to galactose. These earlier methods, however, required venipuncture, preparation of washed, packed red cells, and shipment of the sample in dry ice to a central laboratory. With the present method, capillary blood can be drawn by a nonphysician, applied to filter paper and mailed in a conventional envelope at ambient temperature. From this sample, the Gal-1-P content of the red cells can be determined, if the hematocrit is known. These conveniences should allow estimates of Gal-1-P at a frequency more appropirate for optimal dietary control.