Methemoglobin; Carboxyhemoglobin; Sulfhemoglobin
Hemoglobin derivatives are altered forms of hemoglobin. Hemoglobin is a protein in red blood cells that moves oxygen and carbon dioxide between the lungs and body tissues.
This article discusses the test used to detect and measure the amount of hemoglobin derivatives in your blood.
The test is done using a small needle to collect a sample of blood from an artery. The sample may be collected from an artery in the wrist, groin, or arm.
Before blood is drawn, the health care provider may test circulation to the hand (if the wrist is the site). After the blood is drawn, pressure applied to the puncture site for a few minutes stops the bleeding.
How to Prepare for the Test
No special preparation is needed.
For children, it may help to explain how the test will feel and why it is done. This may make the child feel less nervous.
How the Test will Feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the Test is Performed
This test is used to diagnose carbon monoxide poisoning. It is also used to detect changes in hemoglobin that may result from certain drugs. Some chemicals or drugs can change the hemoglobin so it no longer works properly.
Abnormal forms of hemoglobin include:
Carboxyhemoglobin: An abnormal form of hemoglobin that has attached to carbon monoxide instead of oxygen or carbon dioxide. High amounts of this type of abnormal hemoglobin prevent the normal movement of oxygen by the blood.
Sulfhemoglobin: A rare abnormal form of hemoglobin that can't carry oxygen. It may result from certain medicines such as phenacetin, or sulfonamides.
Methemoglobin: A problem that occurs when the iron that is part of hemoglobin is changed so that it does not carry oxygen well. Certain drugs and other compounds such as nitrites introduced into the blood stream can cause this problem.
The following values represent the percentage of hemoglobin derivatives based on total hemoglobin:
- Carboxyhemoglobin -- less than 1.5% (but may be as high as 9% in smokers)
- Methemoglobin -- less than 2%
- Sulfhemoglobin -- undetectable
Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What Abnormal Results Mean
High levels of hemoglobin derivatives can lead to major health problems. The altered forms of hemoglobin do not allow oxygen to be moved properly through the body. This can lead to tissue death.
The following values, except sulfhemoglobin, represent the percentage of hemoglobin derivatives based on total hemoglobin.
- 10% to 20% -- symptoms of carbon monoxide poisoning begin to appear
- 30% -- severe carbon monoxide poisoning present
- 50% to 80% -- results in potentially deadly carbon monoxide poisoning
- 10% to 25% -- results in bluish skin color (cyanosis)
- 35% to 40% -- results in shortness of breath and headache
- Over 60% -- results in lethargy and stupor
- Over 70% -- may result in death
- Values of 10 grams per deciliter (g/dL) or 6.2 millimoles per liter (mmol/L) cause bluish skin color due to lack of oxygen (cyanosis), but do not cause harmful effects most of the time.
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