Letters to the Editor

Abstract

30 June 2006 Dear Editor, GALACTOSAEMIA PRESENTING AS BEDSIDE HYPERGLYCAEMIA We would like to highlight a clinically significant but little known limitation of bedside glucometers. A male baby was presented to us at 5 weeks of age with failure to thrive. He had initially breastfed but changed to bottle formula feeds rapidly. He had an enlarged liver span on percussion. Bedside blood glucose testing with the accu-chek advantage II meter showed a concentration of 17.9 mmol/L. Urine dipstix was negative for glucose and ketones. A venous blood gas showed a pH of 7.37, bicarbonate 20.1 nmol/L and base excess −4 mEq/L. Laboratory measurement of blood glucose gave a concentration of 3 mmol/L. Urine-reducing substances were strongly positive, with urine glucose remaining negative. A provisional diagnosis of galactosaemia was made and a subsequent galactose-1-phosphate uridyl transferase level showed no enzyme activity, confirming the diagnosis. The baby was established on a soya-based formula and has begun to thrive. Bedside glucose testing meters have made possible immediate recognition of hypo- and hyperglycaemic states. The results obtained from such meters are affected by multiple factors and accuracy is lost at very high and very low blood glucose concentrations. Severe dehydration, hypotension and high haematocrit (>55%) may cause an underestimation of blood glucose concentration.1,2 High estimations of blood glucose may be caused by lipaemic blood, low haematocrit (<25%), sugar on the skin at the venesection point and chemicals in the blood that are measured by the meter.3 Interfering chemicals that the glucometer measures in addition to glucose are listed in the meter’s instructions. Galactose is listed as an interfering substance in the instructions for use supplied with the Roche accu-chek advantage II meter (Roche Diagnostics Limited, Lewes, East Sussex, UK). In our infant, galactose and glucose measured by the bedside meter resulted in the initial impression of hyperglycaemia. Such overestimation of glucose may mask true hypoglycaemia. Newman et al. has previously reported a galactosaemic infant with liver failure whose hypoglycaemia was not verified by the accu-chek advantage II meter.4 Point of care glucose testing is intended to supplement rather than replace laboratory testing. Clinicians should be aware of the specific limitations of the bedside meter that they use and consider these when interpreting results.