Clinical evaluation of a portable lactate meter in type I glycogen storage disease.

High lactate concentrations occur in type I glycogen storage disease (GSD) whenever glycogenolysis occurs. Not only does hyperlactataemia cause acute clinical deterioration, but chronic lactate elevations have also been associated with many of the long-term complications in GSD. A portable finger-stick blood lactate meter has recently been marketed as a training tool for high-performance athletes, but it has not been tested as a clinical diagnostic tool. This study was performed to assess the accuracy of the portable lactate meter in subjects with GSD I who are predisposed to high lactate concentrations. A total of 166 intravenous and 39 capillary samples from 13 subjects were tested concomitantly on three different lactate meters. The meter readings were compared with the lactate concentration determined by the laboratory gold-standard enzymatic colorimetric assay. Almost no inter-meter variability was found. The lactate meter values had outstanding correlation with the laboratory lactate determination, although the meters were found to run 0.5 mmol/L higher than the laboratory assay. The meter deviation was independent of lactate concentration. More variability was noted with finger-stick capillary lactate determinations, but monitoring of trends with capillary samples should prove valuable as a method for determining long-term control or acute deterioration. The portable lactate meter is a highly accurate tool for monitoring lactate concentrations, and should prove valuable for monitoring metabolic control in patients with GSD type I and other disorders associated with hyperlactataemia.