Lactate stress testing in sporadic amyotrophic lateral sclerosis

Mitochondrial dysfunction is frequently observed in ALS. Mitochondrial dysfunction may result in increased serum lactate at rest or low levels of exercise, being used for diagnostic purposes. The study investigated if resting-lactate-determination is superior to lactate-stress-testing (LST) in demonstrating mitochondrial dysfunction in ALS. Included were 15 ALS patients, 4 women, 11 men, aged 37-72. Severity of the disease was assessed by the Norris-score. The control group comprised 66 healthy subjects, 40 women, 26 men, aged 36-76. Serum lactate was determined before, three times during, and once after a constant workload with 30 W on a bicycle ergometer. According to the ElEscorial criteria 8 patients had definite, 4 probable, 3 possible ALS. Resting lactate was increased in 2 patients, 1 with definite and 1 with possible ALS. The LST was abnormal in 5 patients with definite, I with probable and I with possible ALS. The mean Norris-score was 67.8 in patients with abnormal LST and 74.6 in patients with normal LST. In conclusion, the LST is more suitable than restinglactate-determination in demonstrating mitochondrial dysfunction in ALS. The LST suggests mitochondrial dysfunction in half of the ALS patients. Mitochondrial dysfunction in ALS is related to the clinical severity of the disease.