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Co-Oximetry Blood Test

Last updated Sept. 26, 2018

The Co-Oximetry Blood Test is used to determine the percentages in blood of the various forms of hemoglobin, in relation to total hemoglobin. These forms include oxygenated, deoxygenated, carboxy- and methemoglobin.


What are other Names for this Test? (Equivalent Terms)

  • CO-Oximetry Blood Test

What is Co-Oximetry Blood Test? (Background Information)

  • Co-oximetry is a technique that measures the levels of the oxygen-carrying protein hemoglobin, which is the chief component of red blood cells. Co-oximetry is a useful tool in that it helps determine the levels of various forms of hemoglobin
  • Oxygen is extremely important in sustaining human life. It is so important that fully one-third of the body’s 75 trillion cells are red blood cells, the vehicles for oxygen transport
  • The so-called “bed” of these vehicles, the storage part, is hemoglobin. Each red blood cell is 97% hemoglobin, meaning that there is a tremendous amount of hemoglobin present at any one time - around 0.75 kg
  • Iron is necessary to hemoglobin because it serves essential structural and functional roles. Methemoglobin is a form of hemoglobin in which the iron holding the hemoglobin protein together is in the wrong chemical form
  • Carboxyhemoglobin is the name given to hemoglobin that is bound to carbon monoxide instead of oxygen, the molecule that it normally binds. This creates a dangerous condition of carbon monoxide poisoning
  • Carbon monoxide, which is released in vehicle exhaust and tobacco smoke among other sources, interferes with hemoglobin’s ability to transport oxygen. This is because hemoglobin preferentially binds to it instead of to oxygen
  • Carboxyhemoglobin is formed as a result of hemoglobin binding to carbon monoxide, taking oxygen’s place. This is dangerous because the decrease in levels of hemoglobin bound to oxygen impairs the oxygen-carrying capacity of blood. This leads to oxygen deprivation and tissue damage
  • The Co-Oximetry Blood Test is used to determine the percentages in blood of the various forms of hemoglobin, in relation to total hemoglobin. These forms include oxygenated, deoxygenated, carboxy- and methemoglobin
  • The test is used to diagnose possible intoxication and other causes of decreased oxygen availability, or hypoxia
  • The test works by measuring the absorbance of a certain wavelength of light, which correlates with the amount of hemoglobin that is present. The more light of a certain wavelength is absorbed, the more hemoglobin of a given type is present

What are the Clinical Indications for performing the Co-Oximetry Blood Test?

Following are the clinical indications for performing the Co-Oximetry Blood Test:

  • Family history of hemoglobin disorders
  • Monitoring the effects of carbon monoxide poisoning
  • Monitoring the effects of cigarette use
  • Muscle fatigue
  • Nausea
  • Vomiting
  • Blue coloration of the skin
  • Headache
  • Altered mental status
  • Difficulty breathing

How is the Specimen Collected for Co-Oximetry Blood Test?

Following is the specimen collection process for Co-Oximetry Blood Test:

Sample required: Blood

Process of obtaining blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Co-Oximetry Blood Test Result?

A high value for the Co-Oximetry Blood Test may indicate:

  • Carbon monoxide poisoning
  • Congenital hemoglobin disorder

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Certain factors may interfere with the Co-Oximetry Blood Test. These include diet, exercise, and hemolytic disorders

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Jan. 17, 2016
Last updated: Sept. 26, 2018