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Test Code CO Carboxyhemoglobin

Important Note

Specimens cannot be collected by capillary methods.

Additional Codes

Cerner

NextGen

Carboxyhemoglobin

Carboxyhemoglobin

Alternate Name(s)

CO

COHGB

Carbon Monoxide

Useful For

Carboxyhemoglobin (COHb): Indicates exposure to carbon monoxide (CO). Carbon monoxide is a common gaseous poison which combines with hemoglobin in a manner almost identical to oxygen.  Since this bond is 210 times stronger than oxygenated hemoglobin bonding, CO is not readily displaced except at high oxygen tension. 

Methodology

Amperometric

Patient Preparation

None

Collection Instructions

  • Standard phlebotomy practices.
  • Arterial Blood Gas specimens drawn in plastic syringes should not be iced, they should be kept at room temperature and analyzed within 30 minutes of collection (Per NCCLS C46-A, Vol. 21 No.14, Sect 4.2.1.).
  • Place venous specimens on ice and immediately transport to laboratory immediately.Specimen container must be full so that it has the correct heparin/blood ratio.

Specimen Requirements

Minimum Volume

150 µL

Container

Heparinized Syringe free of air bubbles

Or

Lithium Heparin tube

Stability

Room temperature or place on ice immediately for transport and analyze within 30 minutes of collection time.

Rejection Criteria

The Laboratory will not accept specimens in syringes with needles -- the syringe must be capped with a rubber stopper. 

Capillary specimen.

Result Reporting and Reference Values

Reference Range
  • Nonsmoker: 0-3%
  • Smoker: 0-10%

Critical Ranges

>35%

Reflex Testing

None

Limitations

  • Air bubbles must be removed from the sample immediately.  Contamination with room air will affect results.
  • Clotting and dilutional effects may be present if the sample collection technique is not performed correctly.
  • The presence of unknown interfering substances, clots or other foreign matter within the blood sample that alters the optical spectrum will result in higher levels of residual spectrum. A sample with an absorbance error will not be reported.
  • The substances listed below showed an interference with CO-Oximetry/tBili analytes causing a clinically significant error (> TEa).