Carbon dioxide (CO2)

Test Code

CO2

Alias/See Also

Enzymatic Carbonate, CO2, ECO2

Preferred Specimen

1.0 mL plasma (0.5 mL minimum)

Transport Container

PST (light green top). Red top and SST also acceptable

Specimen Stability

Room temperature: 8 hours, Refrigerated: 2 days, Frozen: 6 months

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Grossly hemolyzed specimens are unacceptable.

Reference Range

Age	Female / Male
Adult (>18 years):	21 – 32 mmol/L
Pediatric:
0 – 6 days	13-21
7 – 30 days	13-22
1 – 5 months	13-23
6 – 12 months	14-23
13 - 23 months	16-25
2 – 18 years	21-32

Clinical Significance

Increase in serum CO2 content for the most part reflects increase in serum bicarbonate concentration rather than dissolved CO2 gas (which accounts for only a small fraction of the total). Increased serum bicarbonate is seen in compensated respiratory acidosis and in metabolic alkalosis. Diuretics (thiazides, ethacrynic acid, furosemide, mercurials), corticosteroids (in long term use), and laxatives (when abused) may cause increased bicarbonate.

Decrease in blood CO2 is seen in metabolic acidosis and compensated respiratory alkalosis. Substances causing metabolic acidosis include ammonium chloride, acetazolamide, ethylene glycol, methanol, paraldehyde, and phenformin. Salicylate poisoning is characterized by early respiratory alkalosis followed by metabolic acidosis with attendant decreased bicarbonate.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.