Which analyte commonly requires anaerobic transport to preserve its measured value?

• A. Ammonia
• B. ABG
• C. ACP
• D. Ionized calcium

Answer: (B)

The key idea is how preanalytic handling affects gas measurements. Arterial blood gas values depend on dissolved CO2 and O2, which are extremely sensitive to contact with air. If a blood sample is exposed to the atmosphere, CO2 can diffuse out and O2 can diffuse in, causing the pH to rise and the PaCO2 to fall—distorting the true in vivo values. Transporting the sample in an anaerobic, sealed system (for example, a heparinized syringe with minimal air exposure and often cooled) helps keep CO2, O2, and pH stable until analysis. This is why arterial blood gas samples commonly require anaerobic transport to preserve their measured values. The other analytes aren’t primarily affected by anaerobic conditions: ammonia is mainly sensitive to rapid processing and cooling to stop in vitro production, while ACP and ionized calcium are influenced by handling and pH but not by needing an anaerobic transport environment.