Oral glucose lactate stimulation test in mitochondrial disease

We selected 23 patients with neurologic diseases, including 15 boys and 8 girls from 1 month to 10 years of age, who were divided into mitochondrial and nonmitochondrial disease groups. All patients were required to fast and rest for at least 4-10 hours before the test. Glucose was administered orally using a 50% glucose:water solution at a dose of 1.75 mg/kg. Blood samples then were drawn from a retained heparinized venous line at 0, 30, 60, 120, and 180 min and tested for lactate and glucose levels. Of the mitochondrial disease group, 10 of 11 patients had an upward sloping curve of lactate metabolism; the one who had a flat line response was a patient who suffered from a free-fatty-acid metabolic defect presenting with a recurrent Reye-like syndrome. There was a relatively flat line response in the nonmitochondrial disease group except in a patient with alternating hemiplegia whose symptoms responded well to flunarizine therapy. A significant increase in blood lactate content at 60 min after glucose loading occurred in the mitochondrial disease group, in contrast to that of the nonmitochondrial group. Sensitivity and specificity of a 5 mg/dl increase in blood lactate concentration at 60 min was 72.7% vs. 91.7% Moreover, all 4 patients whose blood lactate increased by 13 mg/dl at 60 min were in the mitochondrial disease group.