Diagnostic yield of the lactate stress test in 160 patients with suspected respiratory chain disorder.

Aim of the present study was to investigate the diagnostic yield of the lactate-stress-test in unselected patients with suspected respiratory-chain disorder (RCD). Serum lactate was determined before, during and after a 15-minute, constant 30W workload on a bicycle in 48 controls and 160 patients with suspected RCD. 122 had definite RCD, 38 neurological disorders other than RCD. The sensitivity, specificity, positive predictive value, negative predictive value and pre-test likelihood of the test was 69, 74, 89, 42 and 76% respectively. In conclusion, the lactate-stress-test proved a powerful tool to assess impaired oxidative metabolism in RCDs.