Estimation, prevention, and quality control of carbon dioxide loss during aerobic sample processing

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Analytical Biochemistry

Background:

• Carbon dioxide (CO2) is a critical analyte in blood gas analysis.
• Pre-analytical variables can significantly affect CO2 measurements.
• Routine laboratory procedures may introduce errors in CO2 quantification.

Purpose of the Study:

• To quantify carbon dioxide loss during serum sample processing.
• To identify factors contributing to pre-analytical CO2 variability.
• To evaluate methods for preventing CO2 loss in clinical samples.

Main Methods:

• Measurement of CO2 levels in serum samples subjected to centrifugation and storage.
• Assessment of CO2 loss under varying conditions (tube fill volume, storage time, air exposure).
• Evaluation of tert-butylamine as a CO2 stabilization agent.

Main Results:

• Routine processing leads to 2–6 mmol/L CO2 loss from serum samples.
• Incomplete filling of collection tubes and prolonged storage increase CO2 loss.
• Extreme CO2 loss (up to 8 mmol/L) observed with open sample exposure.
• Tert-butylamine effectively prevents CO2 loss at optimal concentrations (14–16 mmol/L) and pH (9.0–9.3).

Conclusions:

• Pre-analytical CO2 loss is a significant issue in clinical laboratories.
• Current quality control may not detect clinically relevant CO2 loss.
• Stabilization with tert-butylamine is a viable strategy to ensure accurate CO2 measurements.