Urinary lactate excretion to monitor the efficacy of treatment of type I glycogen storage disease

The purpose of this study was to investigate the usefulness of urinary lact ate measurements to assess the adequacy of dietary treatment in patients wi th type I glycogen storage disease (GSD-I). We determined the correlation o f urine and blood lactate concentrations in 21 GSD-I patients during 24-h a dmissions to the General Clinical Research Center (GCRC) during which hourl y blood samples and aliquots of every void were obtained. In all but 1 pati ent, we found a good correlation between blood lactate concentrations and u rinary lactate excretion. One patient did not excrete lactate in significan t amounts despite elevated blood lactate concentrations. In 17 patients, th e highest blood lactate concentrations occurred during the night. Markedly elevated nighttime average blood lactate concentrations above 3.5 mmol/l re sulted in a urinary lactate concentration above the normal limit of 0.067 m mol/mmol creatinine in the first morning urine specimen. Mildly elevated ni ghttime blood lactate concentrations (between 2.2 and 3.5 mmol/l) led to ur inary lactate concentrations that were either normal or moderately elevated . All patients with normal blood lactate concentrations during the night al so had normal first morning urinary lactate concentrations. The degree of u rinary lactate excretion in relation to blood lactate concentrations varied by individual. Urinary filter paper specimens, collected at home during th e night and in the morning and mailed to the laboratory, were used to monit or the dietary compliance of 5 GSD-I patients at home over a period of 6 to 9 weeks prior to their GCRC admissions. These data suggested variable degr ees of dietary control. In conclusion, the urinary lactate concentration is a useful parameter to monitor therapy of GI SD-I patients at home. To be i nterpretable, the baseline urinary lactate concentration in relation to the blood lactate concentration has to be determined, (C) 2000 Academic Press.