A new method of blood galactose estimation for mass screening of galactosemia.

A new method for quantitative determination of galactose in blood by fluorescence of NADH was described. The assay system consisted of beta-galactose dehydrogenase, NAD, buffer and a denatured blood disc (3 mm diameter), and the reaction was carried out for 1 hr at 37 degrees C. Denaturation of hemoglobin was accomplished by exposing the blood disc to a vapor of formic acid in an air-tight container; this procedure completely eliminated false positive cases of galactosemia. This method can be applied in a wide range of galactose concentration from low (0 mg%) to high levels (200-1,000 mg%) with the accuracy of 8.0 +/- 0.3 mg% from a coefficient of variation of 3.5%. Semi-quantitative assay was also possible by using a spot test like Beutler's method. The galactose content in one disc paper (3 mm diameter) of blood containing 5 mg% galactose is approximately 0.1 micrograms. The newly developed method is satisfactorily applicable in neonatal mass screening and clinical cases.