A new method of screening for inherited disorders of galactose metabolism

A method has been developed for detecting elevated levels of galactose and galactose-1-phosphate in routine blood samples of newborns and has been successfully applied as a screening procedure for galactosemia in several laboratories. The procedure utilizes a strain of Escherichia coli that becomes resistant to bacteriophage C21 in the presence of galactose. The presence of galactose or galactose-1-phosphate is detected as a zone of bacterial growth around blood spots placed on a dish in which the bacteria are otherwise killed by phage. The diameter of the growth zone is proportional to the concentration of total blood galactose. The procedure has the potential of detecting all metabolic abnormalities that can lead to the accumulation of galactose or galactose-1-phosphate. Over a million newborn infants have now been tested by this procedure in three countries. In the New England Regional Screening Program, 12 galactosemic children were detected in 825,403 live births. One additional case, a sibling of a previously diagnosed galactosemic, was not allowed any milk feeding and was detected by an enzymatic test of cord blood. The combined frequency was 1:63,000. No problems of interference by antibiotics were apparent. Use of the test in Switzerland and in Japan also allowed the discovery of infants with UDP galactose 4-epimerase deficiency. Our experience suggests that the test provides an efficient and reliable means of detecting congenital defects of galactose metabolism with a very low frequency of errors. It can also be used to monitor blood galactose levels in the management of galactosemic children.