Hand-held glucose meters are routinely used for measuring point of care (POC) glucose in special care nurseries and emergency departments because of their portability, immediacy of results, and minimal blood volume requirements. These devices use one of the following test methods: glucose dehydrogenase pyrroloquinolinequinone (GDH-PQQ), glucose dehydrogenase nicotinamide adenine dinucleotide (GDH-NAD), glucose oxidase, or glucose hexokinase methods. Accucheck® (Roche) that uses the GDH-PQQ method cannot distinguish glucose, maltose, galactose or xylose from each other, and thus may provide higher anomalous readings. However MediSense Optium glucose analyzer® and the HemoCue B-Glucose analyzer® which also utilize GDH are not affected by galactose(1). This has serious implications and may result in irreversible brain damage following aggressive insulin treatment for elevated glucose reading(2). We report a child with classical galactosemia, in which we commenced insulin drip due to falsely elevated blood sugar levels. Timely thinking for a possibility of error due to portable glucometers prevented a catastrophe from happening.

A two-month old infant, product of non-consanguineous marriage with birth weight of 2.54 kilograms presented with failure to thrive. Clinical examination revealed a malnourished (weight 2.6 kg), irritable child with icterus, mild pallor, cataract in the left eye and firm hepatosplenomegaly. Initial glucose using Accu-check® was elevated (442 mg/dL). Urine for reducing sugars was strongly positive. Child was commenced on insulin drip, thinking of a possibility of diabetes mellitus. There was marked discordance in paired evaluation of sugars using GDH-PQQ method and laboratory estimations using glucose oxidase method (442 and 91 mg/dL and 391 and 42 mf/dL, respectively).

Other investigations suggested conjugated hyperbilirubinemia and deranged liver function test (total bilirubin of 5.24 mg/dL, direct bilirubin 4.22 mg/dL, SGOT 195, SGPT 101 alkaline phosphatase 1420). Urine culture grew Escherichia coli. A diagnosis of galactosemia was anticipated and confirmed by plasma galactose level of 30 mg/dL and markedly reduced galactose transferase enzyme levels 2.34 unit/g (normal value 15-30 unit/g). Epimerase and galactokinase levels were normal. Child showed dramatic improvement on galactose free diet and was discharged with weight of 3.2 kg.

Hand held glucose meters can have marked variability ranging from 3.9 to 10.9% in the mid-l00 mg/dL glucose range and 6.2 to 13.3% in the hypoglycemic range(1,3). Reducing sugars such as galactose, as described in the case above, can interfere with true readings and paradoxically produce higher readings(1,3). Intravenous immunoglobulin solutions, oral xylose, and peritoneal dialysis solutions may contain or be metabolized to maltose, galactose or xylose and thus interfere with the results of glucometers.

We stress the importance of laboratory confirmation of all unexpectedly high readings using hand held glucose meters before initiation of treatment to prevent catastrophes. We also urge the pediatricians to know the method of estimation of their glucometer.

Dr Vinod Chaudhury and Dr Vivek Goswami, Department of Pediatrics at Fortis hospital, Noida and Dr Pankaj Garg at Sitaram Bhartia Institute of Science and Research for help in drafting.