Lactate stress testing by bedside lactate determination.

Lactate determination for the lactate-stress-test (LST) by means of a bedside method has not been performed. Serum lactate was determined by means of the Ektachrome Clinical Chemistry Slide (LST1) and bedside by means of the Acutrend Lactate (LST2) once before, 3 times during, and once after a 15-min, constant 30-W workload on a bicycle in 20 controls, 21 disease controls, and 22 patients with mitochondriopathy (MCP). Lactate's upper reference limits at rest, 5, 10, 15 min after starting, and 15 min after finishing the exercise were 2.0, 1.9, 1.9, 1.8, and 1.5 mmol/L for the LST1 and 2.5, 2.9, 2.5, 2.7, and 2.0 mmol/L for the LST2. The LSTI (LST2) was abnormal in 17 (18) MCP patients, 7 (3) disease controls, and none (none) of the healthy subjects. The sensitivity of the LST1 (LST2) for MCP patients was 77% (82%). The specificity of the LST1 (LST2) was 67% (86%). Sensitivity and specificity of the LST2 are higher than that of the LST1. The LST2 can thus replace the LST1, since it is also easier to handle, quick, reliable, and cheaper.