Not all sugars are equal: galactose interference leading to false hyperglycaemia in a case of classical galactosaemia

Abstract Objectives Classical galactosaemia (OMIM #230400) is an inborn error of carbohydrate metabolism caused by deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT). Case presentation We report a case of a female infant who presented with vomiting, failure to thrive, hepatic transaminitis and a discrepancy between point-of-care (POC) glucometer (Accu-chek ® Inform II, Roche Diagnostics, Germany) and capillary blood glucose (ABL90 Flex Plus © blood gas analyser) testing results, raising the suspicion for a diagnosis of classical galactosaemia. This was attributed to suspected analytical interference from markedly elevated blood galactose, due to a known limitation of the POC glucometer specificity for the monosaccharide sugars glucose and galactose. This led to falsely elevated glucose readings on POC glucometer testing in the presence of a high galactose concentration. Reduced GALT enzyme activity and genetic testing subsequently confirmed a diagnosis of classical galactosaemia. Conclusions Identification of discrepancies in certain POC glucometers and capillary blood gas or venous glucose measurements by the clinical biochemistry laboratory may indicate POC glucometer interference and raise suspicion for a diagnosis of classical galactosaemia in the newborn setting.