Lactate stress testing by bedside lactate determination.

Area of Science:

• Clinical Chemistry
• Exercise Physiology
• Mitochondrial Diseases

Background:

• Lactate determination is crucial for the lactate-stress-test (LST).
• Bedside lactate measurement methods for LST have not been widely evaluated.
• Mitochondriopathy (MCP) diagnosis can be aided by stress testing.

Purpose of the Study:

• To evaluate the performance of a bedside lactate determination method (Acutrend Lactate, LST2) against a standard laboratory method (Ektachrome Clinical Chemistry Slide, LST1) during a lactate-stress-test.
• To compare the sensitivity and specificity of both methods in identifying patients with mitochondriopathy (MCP).

Main Methods:

• A 15-minute, constant 30-W bicycle workload was administered to 20 controls, 21 disease controls, and 22 MCP patients.
• Serum lactate levels were measured using both Ektachrome Clinical Chemistry Slide (LST1) and Acutrend Lactate (LST2) at multiple time points: before, during, and after exercise.
• Lactate's upper reference limits and test performance metrics (sensitivity, specificity) were calculated for both methods.

Main Results:

• The Acutrend Lactate (LST2) showed higher upper reference limits post-exercise compared to LST1.
• LST2 identified more MCP patients (18) and disease controls (3) as abnormal than LST1 (17 MCP patients, 7 disease controls).
• LST2 demonstrated higher sensitivity (82% vs. 77%) and specificity (86% vs. 67%) for detecting MCP compared to LST1.

Conclusions:

• The Acutrend Lactate (LST2) method is more sensitive and specific than the Ektachrome Clinical Chemistry Slide (LST1) for lactate determination during lactate-stress-tests in patients with suspected mitochondriopathy.
• The bedside LST2 method is a reliable, easier-to-handle, quicker, and potentially cheaper alternative to LST1 for clinical use.
• LST2 is recommended to replace LST1 for lactate-stress-testing, particularly in the diagnosis of mitochondrial diseases.