Hemoglobin Test
Hemoglobin Test
Definition
Purpose
Precautions
Description
Preparation
Aftercare
Risks
Normal results
Definition
Hemoglobin is a protein inside red blood cells that carries oxygen. A hemoglobin test reveals how much hemoglobin is in a person’s blood. This information can be used to help physician’s diagnose and monitor anemia (a low hemoglobin level) and polycythemia vera (a high hemoglobin level).
Purpose
A hemoglobin test is performed to determine the amount of hemoglobin in a person’s red blood cells (RBCs). This is important because the amount of oxygen available to tissues depends upon how much oxygen is in the RBCs, and local perfusion of the tissues. Without sufficient hemoglobin, the tissues lack oxygen and the heart and lungs must work harder to compensate.
A low hemoglobin measurement usually means the person has anemia. Anemia results from a decrease in the number, size, or function of RBCs. Common causes include excessive bleeding, a deficiency of iron, vitamin B12, or folic acid, destruction of red cells by antibodies or mechanical trauma, and structurally
KEY TERMS
Anemia— A diminished oxygen carrying capacity caused by a decrease in the size, number, or function of red blood cells.
Hemoglobin— A protein inside red blood cells that carries oxygen to body tissues.
Hypoxia— A decreased amount of oxygen in the tissues.
Polycythemia vera— A disease in which the bone marrow makes too many blood cells.
Protein— A polypeptide chain, or a chain of amino acids linked together.
abnormal hemoglobin. Hemoglobin levels are also decreased due to cancer, kidney diseases, other chronic diseases, and excessive IV fluids. An elevated hemoglobin may be caused by dehydration (decreased water), hypoxia (decreased oxygen), or polycythemia vera. Hypoxia may result from high altitudes, smoking, chronic obstructive lung diseases (such as emphysema), and congestive heart failure. Hemoglobin levels are also used to determine if a person needs a blood transfusion. Usually a person’s hemoglobin must be below 7-8 g/dL before a transfusion is considered, or higher if the person has heart or lung disease. The hemoglobin concentration is also used to determine how many units of packed red blood cells should be transfused. A common rule of thumb is that each unit of red cells should increase the hemoglobin by approximately 1.0–1.5 g/dL.
Precautions
Fluid volume in the blood affects hemoglobin values. Accordingly, the blood sample should not be taken from an arm receiving IV fluid. It should also be noted that pregnant women and people with cirrhosis, a type of permanent liver disease, have extra fluid, which dilutes the blood, decreasing the hemoglobin. Dehydration, a decreased amount of water in the body, concentrates the blood, which may cause an increased hemoglobin result.
Certain drugs such as antibiotics, aspirin, anti-neoplastic drugs, doxapram, indomethacin, sulfonamides, primaquine, rifampin, and trimethadione, may also decrease the hemoglobin level.
A nurse or phlebotomist usually collects the sample by inserting a needle into a vein, or venipuncture, after cleaning the skin, which helps prevent infections.
Description
Hemoglobin is a complex protein composed of four subunits. Each subunit consists of a protein, or polypeptide chain, that enfolds a heme group. Each heme contains iron (Fe2+) that can bind a molecule of oxygen. The iron gives blood its red color. After the first year of life, 95–97% of the hemoglobin molecules contain two pairs of polypeptide chains designated alpha and beta. This form of hemoglobin is called hemoglobin A.
Hemoglobin is most commonly measured in whole blood. Hemoglobin measurement is most often performed as part of a complete blood count (CBC), a test that includes counts of the red blood cells, white blood cells, and platelets (thrombocytes).
Some people inherit hemoglobin with an abnormal structure. The abnormal hemoglobin results from a point mutation in one or both genes that code for the alpha or beta polypeptide chains. Examples of hemoglobin abnormalities resulting from a single amino acid substitution in the beta chain are sickle cell and hemoglobin C disease. Most abnormal hemoglobin molecules can be detected by hemoglobin electrophoresis, which separates hemoglobin molecules that have different electrical charges.
Preparation
No special preparation is required other than cleaning and disinfecting the skin at the puncture site. Blood is collected in a tube by venipuncture. The tube has an anticoagulant in it so that the blood does not clot in the tube, and so that the blood will remain a liquid.
Aftercare
Discomfort or bruising may occur at the puncture site. Pressure to the puncture site until the bleeding stops reduces bruising; warm packs relieve discomfort. Some people feel dizzy or faint after blood has been drawn, and lying down and relaxing for awhile is helpful for these people.
Risks
Other than potential bruising at the puncture site, and/or dizziness, there are usually no complications associated with this test.
Normal results
Normal values vary with age and sex, with women generally having lower hemoglobin values than men. Normal results for men range from 13-18 g/dL. For women the normal range is 12-16 g/dL. Critical limits(panic values) for both males and females are below5.0 g/dL or above 20.0 g/dL.
A low hemoglobin value usually indicates the person has anemia. Different tests are done to discover the cause and type of anemia. Dangerously low hemoglobin levels put a person at risk of a heart attack, congestive heart failure, or stroke. A high hemoglobin value indicates the body may be making too many red blood cells. Other tests are performed to differentiate the cause of the abnormal hemoblogin level. Laboratory scientists perform hemoglobin tests using automated laboratory equipment. Critically high or low levels should be immediately called to the attention of the patient’s doctor.
Resources
BOOKS
Chernecky, Cynthia C. and Barbara J. Berger. Laboratory Tests and Diagnostic Procedures. 3rd ed. Philadelphia: W. B. Saunders Company, 2001.
Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001.
Kjeldsberg, Carl R. Practical Diagnosis of Hematologic Disorders. 3rd ed. Chicago: ASCP Press, 2000.
ORGANIZATIONS
American Association of Blood Banks. 8101 Glenbrook Road, Bethesda, Maryland 20814. (301) 907-6977. Fax: (301) 907-6895. http://www.aabb.org.
OTHER
Uthman, Ed. Blood Cells and the CBC. 2000. [cited February 17, 2003]. http://web2.iadfw.net/uthman/blood_cells.html (accessed june 12, 2008).
Victoria E. DeMoranville
Mark A. Best, M.D.
Hemoglobin Test
Hemoglobin Test
Definition
Hemoglobin is a protein inside red blood cells that carries oxygen. A hemoglobin test reveals how much hemoglobin is in a person's blood. This information can be used to help physician's diagnose and monitor anemia and polycythemia vera, a condition in which the bone marrow produces too many blood cells.
Purpose
A hemoglobin test is performed to determine the amount of hemoglobin in a person's red blood cells (RBCs). This is important because the amount of oxygen available to tissues depends upon how much oxyhemoglobin is in the RBCs, and local perfusion of the tissues. Without sufficient hemoglobin, the tissues lack oxygen and the heart and lungs must work harder to compensate.
A low hemoglobin measurement usually means the person has anemia. Anemia results from a decrease in the number, size, or function of RBCs. Common causes include excessive bleeding, a deficiency of iron, vitamin B12, or folic acid, destruction of red cells by antibodies or mechanical trauma, and structurally abnormal hemoglobin. Hemoglobin levels are also decreased due to cancer, kidney diseases, and excessive IV fluids. An elevated hemoglobin may be caused by dehydration, hypoxia, or polycythemia vera. Hypoxia may result from high altitudes, chronic obstructive lung diseases, and congestive heart failure. Hemoglobin levels are also used to determine if a person needs a blood transfusion. Usually a person's hemoglobin must be below 8 g/dL before a transfusion is considered. The hemoglobin concentration is also used to determine how many units of packed red blood cells should be transfused. A common rule of thumb is that each unit of red cells should increase the hemoglobin by approximately 1.5 g/dL.
Precautions
Fluid volume in the blood affects hemoglobin values. Accordingly, the blood sample should not be taken from an arm receiving IV fluid. It should also be noted that pregnant women and people with cirrhosis have extra fluid, which dilutes the blood, decreasing the hemoglobin. Dehydration concentrates the blood, which may cause an increased hemoglobin result.
Certain drugs such as antibiotics, aspirin, antineoplastic drugs, doxapram, indomethacin, sulfonamides, primaquine, rifampin, and trimethadione, may also decrease the hemoglobin level.
A nurse or phlebotomist usually collects the sample by venipuncture or fingerstick following standard precautions for the prevention of transmission of bloodborne pathogens.
Description
Hemoglobin is a complex protein composed of four subunits. Each subunit consists of a polypeptide chain that enfolds a heme group. Each heme contains iron (Fe2+) which can bind a molecule of oxygen. The iron gives blood its red color. After the first year of life, 95-97% of the hemoglobin molecules contain two pairs of polypeptide chains designated alpha and beta. This form of hemoglobin is called hemoglobin A.
Hemoblogin is most commonly measured by the cyanmethemoblogin method. Whole blood is mixed with a buffered solution of potassium ferricyanide and potassium cyanide. The potassium ferricyanide oxidizes the heme iron forming methemoglobin (Fe3+). This reacts with potassium cyanide forming cyanmethemoglobin which is orange-red. The absorbance of the solution measured at 540 nm is proportional to the hemoglobin concentration. Hemoglobin is most often performed as part of a complete blood count (CBC), a test that includes counts of the red blood cells, white blood cells, and platelets (thrombocytes).
Some people inherit hemoglobin with an abnormal structure. The abnormal hemoglobin results from a point mutation in one or both genes that code for the alpha or beta polypeptide chains. Examples of abnormal hemoglobins resulting from a single amino acid substitution in the beta chain are sickle cell and hemoglobin C disease. Most abnormal hemoglobin molecules can be detected by hemoglobin electrophoresis. This procedure separates hemoglobin molecules with different net charges.
Preparation
No special preparation is required. Blood is collected by venipuncture in a tube containing EDTA anticoagulant after disinfecting the puncture site.
Aftercare
Discomfort or bruising may occur at the puncture site. Pressure to the puncture site until the bleeding stops reduces bruising; warm packs relieve discomfort. Some people feel dizzy or faint after blood has been drawn and should be treated accordingly.
Complications
Other than potential bruising at the puncture site, and/or dizziness, there are no complications associated with this test.
Results
Normal values vary with age and sex, with women generally having lower hemoglobin values than men. Normal results for men range from 13.6-17.2 g/dL. For women the normal range is 12-15 g/dL. Critical limits (panic values) for both males and females are below 5.0 g/dL or above 20.0 g/dL.
KEY TERMS
Anemia— A diminished oxygen carrying capacity caused by a decrease in the size, number, or function of red blood cells.
Hemoglobin— A protein inside red blood cells that carries oxygen to body tissues.
Polycythemia vera— A disease in which the bone marrow makes too many blood cells.
A low hemoglobin value usually indicates the person has anemia. Further tests are done to discover the cause and type of anemia. Dangerously low hemoglobin levels put a person at risk of a heart attack, congestive heart failure, or stroke. A high hemoglobin value indicates the body is making too many red cells. Further tests are performed to differentiate the cause.
Health care team roles
Laboratory scientists perform hemoglobin tests using automated laboratory equipment. Critically high or low levels should be immediately called to the attention of the patient's nurse or doctor. Nurses should bring high or low hemoglobin levels to the attention of the patient's physician, and should also report any signs and symptoms that could be associated with an abnormal hemoglobin: medications, excessive thirst, tachycardia, low blood pressure, weakness, etc.
Resources
BOOKS
Chernecky, Cynthia C., and Berger, Barbara J. Laboratory Tests and Diagnostic Procedures, 3rd ed. Philadelphia: W. B. Saunders Company, 2001.
Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests, 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001.
PERIODICALS
Hsia, Connie C. W. "Respiratory Function of Hemoglobin." New England Journal of Medicine 338 (January 98): 239-247.
Hemoglobin Test
Hemoglobin test
Definition
Hemoglobin is a protein inside red blood cells that carries oxygen. A hemoglobin test reveals how much hemoglobin is in a person's blood. This information can be used to help physician's diagnose and monitor anemia (a low hemoglobin level) and polycythemia vera (a high hemoglobin level).
Purpose
A hemoglobin test is performed to determine the amount of hemoglobin in a person's red blood cells (RBCs). This is important because the amount of oxygen available to tissues depends upon how much oxygen is in the RBCs, and local perfusion of the tissues. Without sufficient hemoglobin, the tissues lack oxygen and the heart and lungs must work harder to compensate.
A low hemoglobin measurement usually means the person has anemia. Anemia results from a decrease in the number, size, or function of RBCs. Common causes include excessive bleeding, a deficiency of iron, vitamin B12, or folic acid, destruction of red cells by antibodies or mechanical trauma, and structurally abnormal hemoglobin. Hemoglobin levels are also decreased due to cancer, kidney diseases, other chronic diseases, and excessive IV fluids. An elevated hemoglobin may be caused by dehydration (decreased water), hypoxia (decreased oxygen), or polycythemia vera. Hypoxia may result from high altitudes, smoking, chronic obstructive lung diseases (such as emphysema), and congestive heart failure. Hemoglobin levels are also used to determine if a person needs a blood transfusion . Usually a person's hemoglobin must be below 7–8 g/dL before a transfusion is considered, or higher if the person has heart or lung disease. The hemoglobin concentration is also used to determine how many units of packed red blood cells should be transfused. A common rule of thumb is that each unit of red cells should increase the hemoglobin by approximately 1.0–1.5 g/dL.
Precautions
Fluid volume in the blood affects hemoglobin values. Accordingly, the blood sample should not be taken from an arm receiving IV fluid. It should also be noted that pregnant women and people with cirrhosis, a type of permanent liver disease, have extra fluid, which dilutes the blood, decreasing the hemoglobin. Dehydration, a decreased amount of water in the body, concentrates the blood, which may cause an increased hemoglobin result.
Certain drugs such as antibiotics , aspirin , antineo-plastic drugs, doxapram, indomethacin, sulfonamides , primaquine, rifampin, and trimethadione, may also decrease the hemoglobin level.
A nurse or phlebotomist usually collects the sample by inserting a needle into a vein, or venipuncture, after cleaning the skin, which helps prevent infections.
Description
Hemoglobin is a complex protein composed of four subunits. Each subunit consists of a protein, or polypeptide chain, that enfolds a heme group. Each heme contains iron (Fe2+) that can bind a molecule of oxygen. The iron gives blood its red color. After the first year of life, 95-97% of the hemoglobin molecules contain two pairs of polypeptide chains designated alpha and beta. This form of hemoglobin is called hemoglobin A.
Hemoglobin is most commonly measured in whole blood. Hemoglobin measurement is most often performed as part of a complete blood count (CBC), a test that includes counts of the red blood cells, white blood cells, and platelets (thrombocytes).
Some people inherit hemoglobin with an abnormal structure. The abnormal hemoglobin results from a point mutation in one or both genes that code for the alpha or beta polypeptide chains. Examples of hemoglobin abnormalities resulting from a single amino acid substitution in the beta chain are sickle cell and hemoglobin C disease. Most abnormal hemoglobin molecules can be detected by hemoglobin electrophoresis, which separates hemoglobin molecules that have different electrical charges.
Preparation
No special preparation is required other than cleaning and disinfecting the skin at the puncture site. Blood is collected in a tube by venipuncture. The tube has an anticoagulant in it so that the blood does not clot in the tube, and so that the blood will remain a liquid.
Aftercare
Discomfort or bruising may occur at the puncture site. Pressure to the puncture site until the bleeding stops reduces bruising; warm packs relieve discomfort. Some people feel dizzy or faint after blood has been drawn, and lying down and relaxing for awhile is helpful for these people.
Risks
Other than potential bruising at the puncture site, and/or dizziness, there are usually no complications associated with this test.
Normal results
Normal values vary with age and sex, with women generally having lower hemoglobin values than men. Normal results for men range from 13–18 g/dL. For women the normal range is 12–16 g/dL. Critical limits (panic values) for both males and females are below 5.0 g/dL or above 20.0 g/dL.
A low hemoglobin value usually indicates the person has anemia. Different tests are done to discover the cause and type of anemia. Dangerously low hemoglobin levels put a person at risk of a heart attack, congestive heart failure, or stroke. A high hemoglobin value indicates the body may be making too many red blood cells. Other tests are performed to differentiate the cause of the abnormal hemoblogin level. Laboratory scientists perform hemoglobin tests using automated laboratory equipment. Critically high or low levels should be immediately called to the attention of the patient's doctor.
Resources
books
Chernecky, Cynthia C. and Barbara J. Berger. Laboratory Tests and Diagnostic Procedures. 3rd ed. Philadelphia: W. B. Saunders Company, 2001.
Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests. 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001.
Kjeldsberg, Carl R. Practical Diagnosis of Hematologic Disorders. 3rd ed. Chicago: ASCP Press, 2000.
organizations
American Association of Blood Banks. 8101 Glenbrook Road, Bethesda, Maryland 20814. (301) 907-6977. Fax: (301) 907-6895. <http://www.aabb.org>.
other
Uthman, Ed. Blood Cells and the CBC. 2000 [cited February 17, 2003]. <http://web2.iadfw.net/uthman/blood_cells.html>.
Victoria E. DeMoranville
Mark A. Best, M.D.
Hemoglobin Test
Hemoglobin Test
Definition
Hemoglobin is a protein inside red blood cells that carries oxygen throughout the body. A hemoglobin test reveals how much hemoglobin is in a person's blood, helping to diagnose and monitor anemia and polycythemia vera.
Purpose
A hemoglobin test is done when a person is ill or during a general physical examination. Good health requires an adequate amount of hemoglobin. The amount of oxygen in the body tissues depends on how much hemoglobin is in the red cells. Without enough hemoglobin, the tissues lack oxygen and the heart and lungs must work harder to try to compensate.
If the test indicates a "less than" or "greater than" normal amount of hemoglobin, the cause of the decrease or increase must be discovered. A low hemoglobin usually means the person has anemia. Anemia results from conditions that decrease the number or size of red cells, such as excessive bleeding, a dietary deficiency, destruction of cells because of a transfusion reaction or mechanical heart valve, or an abnormally formed hemoglobin.
A high hemoglobin may be caused by polycythemia vera, a disease in which too many red blood cells are made.
Hemoglobin levels also help determine if a person needs a blood transfusion. Usually a person's hemoglobin must be below 8 gm/dl before a transfusion is considered.
Description
Hemoglobin is made of heme, an iron compound, and globin, a protein. The iron gives blood its red color. Hemoglobin tests make use of this red color. A chemical is added to a sample of blood to make the red blood cells burst. When they burst, the red cells release hemoglobin into the surrounding fluid, coloring it clear red. By measuring the color using an instrument called a spectrophotometer, the amount of hemoglobin is determined.
Hemoglobin is often ordered as part of a complete blood count (CBC), a test that includes other blood cell measurements.
Some people inherit hemoglobin with an abnormal structure. These abnormal hemoglobins cause diseases, such as sickle cell or Hemoglobin C disease. Special tests, using a process called hemoglobin electrophoresis, identify abnormal hemoglobins.
Preparation
This test requires 5 mL of blood. A healthcare worker ties a tourniquet on the person's upper arm, locates a vein in the inner elbow region, and inserts a needle into that vein. Vacuum action draws the blood through the needle into an attached tube. Collection of the sample takes only a few minutes.
The person should avoid smoking before this test as smoking can increase hemoglobin levels.
Aftercare
Discomfort or bruising may occur at the puncture site or the person may feel dizzy or faint. Pressure to the puncture site until the bleeding stops reduces bruising. Warm packs to the puncture site relieve discomfort.
Normal results
Normal values vary with age and sex. Women generally have lower hemoglobin values than men. Men have 14.0-18.0 g/dL, while women have levels of 12.0-16.0 g/dL.
Abnormal results
A low hemoglobin usually indicates the person has anemia. Further tests are done to discover the cause and type of anemia. Dangerously low hemoglobin levels put a person at risk of a heart attack, congestive heart failure, or stroke.
A high hemoglobin indicates the body is making too many red cells. Further tests are done to see if this is caused by polycythemia vera, or as a reaction to illness, high altitudes, heart failure, or lung disease.
Fluid volume in the blood affects hemoglobin values. Pregnant women and people with cirrhosis have extra fluid, which dilutes the blood, decreasing the hemoglobin. Dehydration concentrates the blood, increasing the hemoglobin.
Resources
PERIODICALS
Hsia, Connie C. W. "Respiratory Function of Hemoglobin." New England Journal of Medicine 338 (January 1998): 239-247.
KEY TERMS
Anemia— A condition characterized by a decrease in the size or number of red blood cells.
Hemoglobin— A protein inside red blood cells that carries oxygen to body tissues.
Polycythemia vera— A disease in which the bone marrow makes too many red blood cells.