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Carbon Dioxide (CO2)

Bicarbonate, CO₂ Content, ctCO₂, TCO₂

Test Codes

EPIC: LAB5131, Beaker: CO2

Department

Chemistry

Instructions

Note: Specimens should be kept tightly closed since CO₂ will diffuse out if the tube is uncapped. This will cause an erroneously decreased value.

Specimen Collection Criteria

FOR EC AND INPATIENT SAMPLE COLLECTION ONLY:

Preferred Sample:  One Light Green (Mint) Top Plasma Separator Tube (PST). (Minimum Whole Blood: 4.0 mL) 

Acceptable Sample:  One Gold Top SST (Minimum Whole Blood: 4.0 mL) 

Do NOT use Dark Green-top Lithium or Sodium Heparin tubes.

FOR PHYSICIAN OFFICE/OUTREACH SAMPLE COLLECTION:

COLLECT:  One Gold Top SST (Minimum Whole Blood:  4.0 mL) 

Contact Laboratory for acceptability of other tube types.
See Minimum Pediatric Specimen Requirements for Microtainer^® collection.

Physician Office/Draw Specimen Preparation

Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection.

Preparation for Courier Transport

Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Rejection Criteria

Moderate to grossly hemolyzed specimens.

Red-top tubes with serum not separated from cells within two hours of collection.

In-Lab Processing

Let SST specimens clot 30-60 minutes. Centrifuge SST tubes and Microtainers^® to separate serum from cells. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Farmington Hills, Grosse Pointe, Royal Oak & Troy

Centrifuged SST Tubes and Microtainers^® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 72 hours
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers^® without Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 72 hours
Frozen (-20°C/-4°F or below): 7 days

Laboratory

Canton Chemistry Laboratory
Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory 
Grosse Pointe Chemistry Laboratory 
Livonia Main Laboratory
Lenox Main Laboratory
Royal Oak Automated Chemistry Laboratory 
Troy Chemistry Laboratory
Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Wayne Chemistry Laboratory 

Performed

Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 4 hours.

Reference Range

OLD:
0 - 1 year:      17 – 27 mmol/L.
1 - 13 years:  20 – 29 mmol/L.
> 13 years:    22 – 32 mmol/L.

CURRENT:
0 - <1 year:    20 – 28 mmol/L.
1 - 13 years:    17 – 28 mmol/L.
> 13 years:     20 – 29 mmol/L. 

Test Methodology

Spectrophotometry, Potentiometry.

Interpretation

• Increased results may indicate respiratory acidosis with CO₂ retention, or metabolic alkalosis.
• Decreased values may indicate respiratory alkalosis or metabolic acidosis, eg, diabetes with ketoacidosis.
• Interpretation requires clinical information and other electrolyte data.

Clinical Utility

The CO₂ assay aids in the evaluation of acid-base balance.

CPT Codes

82374
LOINC:  2019-8, 2028-9

Contacts

Last Updated

10/2/2023