Agreement between peripheral venous and arterial lactate levels

Area of Science:

• Emergency Medicine
• Clinical Chemistry
• Biomarker Analysis

Background:

• Arterial lactate (A-LACT) is a critical biomarker for assessing tissue hypoperfusion and metabolic distress.
• Peripheral venous lactate (V-LACT) offers a less invasive alternative, but its reliability compared to A-LACT requires validation.
• Hyperlactacidemia is a significant indicator of critical illness, necessitating accurate and accessible diagnostic methods.

Purpose of the Study:

• To evaluate the potential of peripheral venous lactate (V-LACT) measurements as a substitute for arterial lactate (A-LACT) in identifying arterial hyperlactacidemia.
• To determine the correlation and agreement between paired A-LACT and V-LACT measurements in an emergency department (ED) setting.
• To assess the diagnostic performance of V-LACT in predicting elevated A-LACT levels.

Main Methods:

• A prospective study comparing simultaneous A-LACT and V-LACT measurements in 74 ED patients.
• Convenience sampling was employed at an urban, public teaching hospital.
• Statistical analysis included correlation (r²), agreement assessment (95% CI for difference), sensitivity, specificity, and likelihood ratios, with A-LACT as the criterion standard.

Main Results:

• A strong correlation (r² = .89) was observed between A-LACT and V-LACT, unaffected by tourniquet time or blood draw timing.
• The mean difference between V-LACT and A-LACT was minimal (.22 mmol/L), but the 95% agreement range was wide (-1.3 to 1.7 mmol/L).
• V-LACT demonstrated 94% sensitivity but only 57% specificity for detecting arterial hyperlactacidemia, with a negative likelihood ratio of 0.1 and positive likelihood ratio of 2.2.

Conclusions:

• While peripheral venous lactate (V-LACT) shows high correlation with arterial lactate (A-LACT), their agreement is imperfect, limiting direct substitution.
• A normal V-LACT reading substantially reduces the likelihood of arterial hyperlactacidemia.
• Caution is advised for routine V-LACT use as a replacement for A-LACT due to potential discrepancies, especially with elevated venous readings.