Lactate-stress testing in 54 patients with mitochondriopathy

Since there are only few data available about the lactate stress test in a group of patients with mitochondrial myopathy, we investigated the sensitiv ity of this test in a larger cohort of such patients. Serum lactate was det ermined before, during and after a 15 minute, constant 30 W workload on a b icycle ergometer in 47 controls, aged 15 to 72 years and 54 patients with m itochondrial myopathy, aged 15 to 74 years. Lactate's upper reference limit s at rest, 5, 10, 15 minutes after starting, and 15 minutes after finishing the exercise were 2.0, 2.1, 2.1, 2.1 and 1.8 mmol/l respectively. The sens itivity of the lactate-stress test was 69%. The lactate-stress test complem ents electrophysiological and bioptical findings and proved to be helpful i n diagnosing mitochondrial myopathy.