Red blood cells are biconcave, disc-shaped cells that transport oxygen from the lungs to body cells. They circulate around the body in the blood and also remove carbon dioxide to the lungs for exhalation. Their red colour comes from the oxygen-carrying protein haemoglobin. Red blood cells are the most abundant cell in the blood. They have no nucleus and are about 7 micrometres in diameter. Magnification: x1650 when printed 10 centimetres wide.

Blood tests are very common. When you have routine checkups, your doctor may recommend blood tests to see how your body is working.

Many blood tests don’t require any special preparations. For some, you may need to fast (not eat any food) for 8 to 12 hours before the test. Your doctor will let you know how to prepare for blood tests.

During a blood test, a small amount of blood is taken from your body. It’s usually drawn from a vein in your arm using a needle. A finger prick also may be used. The procedure usually is quick and easy, although it may cause some short-term discomfort. Most people don’t have serious reactions to having blood drawn.

Lab workers draw the blood and analyze it. They use either whole blood to count blood cells, or they separate the blood cells from the fluid that contains them. This fluid is called plasma or serum.

The fluid is used to measure different substances in the blood. The results can help detect health problems in early stages, when treatments or lifestyle changes may work best.

However, blood tests alone can’t be used to diagnose many diseases or medical problems. Your doctor may consider other factors, such as your signs and symptoms, your medical history, and results from other tests and procedures, to confirm a diagnosis.

Blood tests help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working.

Specifically, blood tests can help doctors:

• Evaluate how well organs, like the kidneys, liver, and heart, are working
• Diagnose diseases and conditions such as cancer, HIV/AIDS, diabetes, anemia (uh-NEE-me-eh), and coronary heart disease (also called coronary artery disease)
• Learn whether you have risk factors for heart disease
• Check whether medicines you’re taking are working

Blood tests have few risks. Most complications are minor and go away shortly after the tests are done.

Source: National Heart, Lung and Blood Institute

Normal red blood cells are disc-shaped and look like doughnuts without holes in the center. They move easily through your blood vessels. Red blood cells contain hemoglobin (HEE-muh-glow-bin), an iron-rich protein that gives blood its red color. Hemoglobin carries oxygen from the lungs to the rest of the body.

Sickle cells contain abnormal hemoglobin that causes the cells to have a sickle, or crescent, shape. These cells don’t move easily through your blood vessels. They’re stiff and sticky and tend to form clumps and get stuck in the blood vessels. (Other cells also may play a role in this clumping process.)

The clumps of sickle cells block blood flow in the blood vessels in the limbs and organs. Blocked blood vessels can cause pain, serious infections, and organ damage.

Normal Red Blood Cells and Sickle Cells

Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Figure B shows abnormal, sickled red blood cells clumping and blocking blood flow in a blood vessel. (Other cells also may play a role in this clumping process.) The inset image shows a cross-section of a sickle cell with abnormal hemoglobin forming abnormal strands.
Overview

Sickle cell anemia is one type of anemia. Anemia is a condition in which your blood has a lower than normal number of red blood cells. This condition also can occur if your red blood cells don’t contain enough hemoglobin.

Red blood cells are made in the spongy marrow inside the large bones of the body. Bone marrow is always making new red blood cells to replace old ones. Normal red blood cells live about 120 days in the bloodstream and then die. They carry oxygen and remove carbon dioxide (a waste product) from your body.

In sickle cell anemia, the number of red blood cells is low because sickle cells don’t last very long. Sickle cells usually die after only about 10 to 20 days. The bone marrow can’t make new red blood cells fast enough to replace the dying ones.

Sickle cell anemia is an inherited, lifelong disease. People who have the disease are born with it. They inherit two copies of the sickle cell gene—one from each parent.

People who inherit a sickle cell gene from one parent and a normal gene from the other parent have a condition called sickle cell trait.

Sickle cell trait is different than sickle cell anemia. People who have sickle cell trait don’t have the disease, but they have one of the genes that cause it. Like people who have sickle cell anemia, people who have sickle cell trait can pass the sickle cell gene on to their children.
Outlook

Sickle cell anemia has no widely available cure. However, treatments can help with the symptoms and complications of the disease. Blood and marrow stem cell transplants may offer a cure for a small number of people.

Over the past 100 years, doctors have learned a great deal about sickle cell anemia. They know its causes, how it affects the body, and how to treat many of its complications.

Sickle cell anemia varies from person to person. Some people who have the disease have chronic (long-term) pain or fatigue (tiredness). However, with proper care and treatment, many people who have the disease can have improved quality of life and reasonable health much of the time.

Due to improved treatments and care, people who have sickle cell anemia are now living into their forties or fifties, or longer.

Complete Blood Count

The CBC is one of the most common blood tests. It’s often done as part of a routine checkup.

The CBC can help detect blood diseases and disorders, such as anemia, infections, clotting problems, blood cancers, and immune system disorders. This test measures many different parts of your blood, as discussed in the following paragraphs.

Red Blood Cells

Red blood cells carry oxygen from your lungs to the rest of your body. Abnormal red blood cell levels may be a sign of anemia, dehydration (too little fluid in the body), bleeding, or another disorder.

White Blood Cells

White blood cells are part of your immune system, which fights infections and diseases. Abnormal white blood cell levels may be a sign of infection, blood cancer, or an immune system disorder.

A CBC measures the overall number of white blood cells in your blood. A CBC with differential looks at the amounts of different types of white blood cells in your blood.

Platelets

Platelets (PLATE-lets) are blood cell fragments that help your blood clot. They stick together to seal cuts or breaks on blood vessel walls and stop bleeding.

Abnormal platelet levels may be a sign of a bleeding disorder (not enough clotting) or a thrombotic disorder (too much clotting).

Hemoglobin

Hemoglobin (HEE-muh-glow-bin) is an iron-rich protein in red blood cells that carries oxygen. Abnormal hemoglobin levels may be a sign of anemia, sickle cell anemia, thalassemia (thal-a-SE-me-ah), or other blood disorders.

If you have diabetes, excess glucose in your blood can attach to hemoglobin and raise the level of hemoglobin A1c.

Hematocrit

Hematocrit (hee-MAT-oh-crit) is a measure of how much space red blood cells take up in your blood. A high hematocrit level might mean you’re dehydrated. A low hematocrit level might mean you have anemia. Abnormal hematocrit levels also may be a sign of a blood or bone marrow disorder.

Mean Corpuscular Volume

Mean corpuscular (kor-PUS-kyu-lar) volume (MCV) is a measure of the average size of your red blood cells. Abnormal MCV levels may be a sign of anemia or thalassemia.

Blood Chemistry Tests/Basic Metabolic Panel

The basic metabolic panel (BMP) is a group of tests that measures different chemicals in the blood. These tests usually are done on the fluid (plasma) part of blood. The tests can give doctors information about your muscles (including the heart), bones, and organs, such as the kidneys and liver.

The BMP includes blood glucose, calcium, and electrolyte tests, as well as blood tests that measure kidney function. Some of these tests require you to fast (not eat any food) before the test, and others don’t. Your doctor will tell you how to prepare for the test(s) you’re having.

Blood Glucose

Glucose is a type of sugar that the body uses for energy. Abnormal glucose levels in your blood may be a sign of diabetes.

For some blood glucose tests, you have to fast before your blood is drawn. Other blood glucose tests are done after a meal or at any time with no preparation.

Calcium

Calcium is an important mineral in the body. Abnormal calcium levels in the blood may be a sign of kidney problems, bone disease, thyroid disease, cancer, malnutrition, or another disorder.

Electrolytes

Electrolytes are minerals that help maintain fluid levels and acid-base balance in the body. They include sodium, potassium, bicarbonate, and chloride.

Abnormal electrolyte levels may be a sign of dehydration, kidney disease, liver disease, heart failure, high blood pressure, or other disorders.

Kidneys

Blood tests for kidney function measure levels of blood urea nitrogen (BUN) and creatinine (kre-AT-ih-neen). Both of these are waste products that the kidneys filter out of the body. Abnormal BUN and creatinine levels may be signs of a kidney disease or disorder.

Blood Enzyme Tests

Enzymes are chemicals that help control chemical reactions in your body. There are many blood enzyme tests. This section focuses on blood enzyme tests used to check for heart attack. These include troponin and creatine (KRE-ah-teen) kinase (CK) tests.

Troponin

Troponin is a muscle protein that helps your muscles contract. When muscle or heart cells are injured, troponin leaks out, and its levels in your blood rise.

For example, blood levels of troponin rise when you have a heart attack. For this reason, doctors often order troponin tests when patients have chest pain or other heart attack signs and symptoms.

Creatine Kinase

A blood product called CK-MB is released when the heart muscle is damaged. High levels of CK-MB in the blood can mean that you’ve had a heart attack.

Blood Tests To Assess Heart Disease Risk

A lipoprotein panel is a blood test that can help show whether you’re at risk for coronary heart disease (CHD). This test looks at substances in your blood that carry cholesterol.

A lipoprotein panel gives information about your:

• Total cholesterol.
• LDL (“bad”) cholesterol. This is the main source of cholesterol buildup and blockages in the arteries. (For more information about blockages in the arteries, go to the Diseases and Conditions Index Atherosclerosis article.)
• HDL (“good”) cholesterol. This type of cholesterol helps decrease blockages in the arteries.
• Triglycerides. Triglycerides are a type of fat in your blood.

A lipoprotein panel measures the levels of LDL and HDL cholesterol and triglycerides in your blood. Abnormal cholesterol and triglyceride levels may be signs of increased risk for CHD.

Most people will need to fast for 9 to 12 hours before a lipoprotein panel.

Source: NHLBI, NIH

SEM blood cells.jpg This is a scanning electron microscope image from normal circulating human blood. One can see red blood cells, several white blood cells including lymphocytes, a monocyte, a neutrophil, and many small disc-shaped platelets. Red cells are nonnucleated and contain hemoglobin, an important protein which contains iron and allows the cell to carry oxygen to other parts of the body. They also carry carbon dioxide away from peripheral tissue to the lungs where it can be exhaled. The infection-fighting white blood cells are classified in two main groups: granular and agranular. Granulocytes are formed in bone marrow; agranulocytes are produced by lymph nodes and spleen. There are two types of agranulocytes: lymphocytes, which fight disease by producing antibodies and thus destroying foreign material, and monocytes. Platelets are tiny cells formed in bone marrow and are necessary for blood clotting.

Hematology is the branch of medicine concerned with the study of blood, the blood-forming organs, and blood diseases. Hematology includes the study of etiology, diagnosis, treatment, prognosis, and prevention of blood diseases. The laboratory work that goes into the study of blood is frequently performed by a medical technologist. Hematologists physicians also very frequently do further study in oncology – the medical treatment of cancer.

Blood diseases affect the production of blood and its components, such as blood cells, hemoglobin, blood proteins, the mechanism of coagulation, etc.

Physicians specialized in hematology are known as hematologists. Their routine work mainly includes the care and treatment of patients with hematological diseases, although some may also work at the hematology laboratory viewing blood films and bone marrow slides under the microscope, interpreting various hematological test results. In some institutions, hematologists also manage the hematology laboratory. Physicians who work in hematology laboratories, and most commonly manage them, are pathologists specialized in the diagnosis of hematological diseases, referred to as hematopathologists. Hematologists and hematopathologists generally work in conjunction to formulate a diagnosis and deliver the most appropriate therapy if needed. Hematology is a distinct subspecialty of internal medicine, separate from but overlapping with the subspecialty of medical oncology. Hematologists may specialize further or have special interests, for example in:

• treating bleeding disorders such as hemophilia and idiopathic thrombocytopenic purpura
• treating hematological malignacies such as lymphoma and leukemia
• treating hemoglobinopathies
• in the science of blood transfusion and the work of a blood bank
• in bone marrow and stem cell transplantation

Source: Wikipedia, Wikimedia

Blood transfusions are done to replace blood lost during surgery or due to a serious injury. A transfusion also may be done if your body can’t make blood properly because of an illness.

During a blood transfusion, a small needle is used to insert an IV line into one of your blood vessels. Through this line, you receive healthy blood. The procedure usually takes 1 to 4 hours, depending on how much blood you need.

Blood transfusions are very common. Each year, almost 5 million Americans need a blood transfusion. Most blood transfusions go well. Mild complications can occur. Very rarely, serious problems develop.

Important Information About Blood

The heart pumps blood through a network of arteries and veins throughout the body. Blood has many vital jobs. It carries oxygen and other nutrients to your body’s organs and tissues. Having a healthy supply of blood is important to your overall health.

Blood is made up of various parts, including red blood cells, white blood cells, platelets (PLATE-lets), and plasma. Blood is transfused either as whole blood (with all its parts) or, more often, as individual parts.

Blood Types

Every person has one of the following blood types: A, B, AB, or O. Also, every person’s blood is either Rh-positive or Rh-negative. So, if you have type A blood, it’s either A positive or A negative.

The blood used in a transfusion must work with your blood type. If it doesn’t, antibodies (proteins) in your blood attack the new blood and make you sick.

Type O blood is safe for almost everyone. About 40 percent of the population has type O blood. People who have this blood type are called universal donors. Type O blood is used for emergencies when there’s no time to test a person’s blood type.

People who have type AB blood are called universal recipients. This means they can get any type of blood.

If you have Rh-positive blood, you can get Rh-positive or Rh-negative blood. But if you have Rh-negative blood, you should only get Rh-negative blood. Rh-negative blood is used for emergencies when there’s no time to test a person’s Rh type.

Blood Banks

Blood banks collect, test, and store blood. They carefully screen all donated blood for possible infectious agents, such as viruses, that could make you sick. (For more information, see “What Are the Risks of a Blood Transfusion?”)

Blood bank staff also screen each blood donation to find out whether it’s type A, B, AB, or O and whether it’s Rh-positive or Rh-negative. Getting a blood type that doesn’t work with your own blood type will make you very sick. That’s why blood banks are very careful when they test the blood.

To prepare blood for a transfusion, some blood banks remove white blood cells. This process is called white cell or leukocyte (LU-ko-site) reduction. Although rare, some people are allergic to white blood cells in donated blood. Removing these cells makes allergic reactions less likely.

Not all transfusions use blood donated from a stranger. If you’re going to have surgery, you may need a blood transfusion because of blood loss during the operation. If it’s surgery that you’re able to schedule months in advance, your doctor may ask whether you would like to use your own blood, rather than donated blood.

If you choose to use your own blood, you will need to have blood drawn one or more times prior to the surgery. A blood bank will store your blood for your use.

Alternatives to Blood Transfusions

Researchers are trying to find ways to make blood. There’s currently no man-made alternative to human blood. However, researchers have developed medicines that may help do the job of some blood parts.

For example, some people who have kidney problems can now take a medicine called erythropoietin that helps their bodies make more red blood cells. This means they may need fewer blood transfusions.

Surgeons try to reduce the amount of blood lost during surgery so that fewer patients need blood transfusions. Sometimes they can collect and reuse the blood for the patient.

Source: National Heart, Lung and Blood Institute

FA prevents your bone marrow from making enough new blood cells for your body to work normally. FA also can cause your bone marrow to make many abnormal blood cells. This can lead to serious health problems, such as leukemia (a type of blood cancer).

FA is a blood disorder, but it also can affect many of your body’s organs, tissues, and systems. Children who inherit FA are at higher risk of being born with birth defects. People who have FA are at higher risk of some cancers and other serious health problems.

FA is different from Fanconi syndrome. Fanconi syndrome affects the kidneys. It’s a rare and serious condition that mostly affects children. Children who have Fanconi syndrome pass large amounts of key nutrients and chemicals through their urine, which leads to serious health and developmental problems.

Bone Marrow and Blood

Bone marrow is the spongy red tissue inside the large bones of your body. Healthy bone marrow contains stem cells that develop into the three types of blood cells that the body needs:

• Red blood cells, which carry oxygen to all parts of your body. Red blood cells also remove carbon dioxide (a waste product) from your body’s cells and carry it to the lungs to be exhaled.
• White blood cells, which help your body fight infections.
• Platelets (PLATE-lets), which help your blood clot.

It’s normal for blood cells to die. The lifespan of red blood cells is about 120 days. White blood cells live less than 1 day. Platelets live about 6 days. As a result, your bone marrow must constantly make new blood cells.

If your bone marrow can’t make enough new blood cells to replace the ones that die, you can have serious health problems.

Fanconi Anemia and Your Body

FA is one of many types of anemia. The term “anemia” usually refers to a condition in which the blood has a lower than normal number of red blood cells.

FA is a type of aplastic anemia. In aplastic anemia, the bone marrow stops making or doesn’t make enough of all three types of blood cells. Low levels of the three types of blood cells can harm many of the body’s organs, tissues, and systems.

With too few red blood cells, your body’s tissues won’t get enough oxygen to work well. With too few white blood cells, your body may have problems fighting infections. This can make you sick more often and make infections worse. With too few platelets, you may suffer from excessive bleeding.

Outlook

If you or your child has FA, you face a greater risk than other people for some cancers. About 10 percent of people who have FA develop leukemia.

People who have FA and survive to adulthood are much more likely than others to develop cancerous solid tumors. The risk of solid tumors increases with age in people who have FA. These tumors can develop in the mouth, tongue, throat, or esophagus (the passage leading from the mouth to the stomach).

Women who have FA are at much greater risk of developing tumors in the reproductive organs than women who don’t have the disease.

FA is an unpredictable disease. The average lifespan for people who have FA is between 20 and 30 years. The most common causes of death related to FA are bone marrow failure, leukemia, and solid tumors.

New medical advances have improved the chances of surviving longer with FA. Blood and marrow stem cell transplant is the major advance in treatment. However, even with this treatment, the risk of some cancers is greater in people who have FA.

Source: National Heart, Lung and Blood Institute

Red blood cells carry oxygen to all parts of your body. They also carry carbon dioxide (a waste product) to your lungs to be exhaled. White blood cells help your body fight infections. Platelets are blood cell fragments that stick together to seal small cuts or breaks on blood vessel walls and stop bleeding.

It’s normal for blood cells to die. The lifespan of red blood cells is about 120 days. White blood cells live less than a day. Platelets live about 6 days. As a result, your bone marrow must constantly make new blood cells.

If your bone marrow can’t make enough new blood cells, many health problems can occur. These problems include irregular heartbeats called arrhythmias (ah-RITH-me-ahs), an enlarged heart, heart failure, infections, and bleeding. Severe aplastic anemia can even cause death.

Overview

Aplastic anemia is a type of anemia. The term “anemia” usually refers to a condition in which your blood has a lower than normal number of red blood cells. Anemia also can occur if your red blood cells don’t contain enough hemoglobin (HEE-muh-glow-bin). This iron-rich protein helps carry oxygen to your body.

In people who have aplastic anemia, the body doesn’t make enough red blood cells, white blood cells, and platelets. This is because the bone marrow’s stem cells are damaged. (Aplastic anemia also is called bone marrow failure.)

Many diseases, conditions, and factors can damage the stem cells. These conditions can be acquired or inherited. “Acquired” means you aren’t born with the condition, but you develop it. “Inherited” means your parents passed the gene for the condition on to you.

In many people who have aplastic anemia, the cause is unknown.

Outlook

Aplastic anemia is a rare but serious disorder. It can develop suddenly or slowly. The disorder tends to get worse over time, unless its cause is found and treated. Treatments for aplastic anemia include blood transfusions, blood and marrow stem cell transplants, and medicines.

With prompt and proper care, many people who have aplastic anemia can be successfully treated. Blood and marrow stem cell transplants may offer a cure for some people who have aplastic anemia.

Source: National Heart, Lung and Blood Institute

Anemia also can occur if your red blood cells don’t contain enough hemoglobin (HEE-muh-glow-bin). Hemoglobin is an iron-rich protein that gives blood its red color. This protein helps red blood cells carry oxygen from the lungs to the rest of the body.

If you have anemia, your body doesn’t get enough oxygen-rich blood. As a result, you may feel tired and have other symptoms. Severe or long-lasting anemia can damage the heart, brain, and other organs of the body. Very severe anemia may even cause death.

Anemia Overview

Blood is made up of various parts, including red blood cells, white blood cells, platelets (PLATE-lets), and plasma (the fluid portion of blood).

Red blood cells are disc-shaped and look like doughnuts without holes in the center. They carry oxygen and remove carbon dioxide (a waste product) from your body. These cells are made in the bone marrow—a sponge-like tissue inside the bones.

White blood cells and platelets (PLATE-lets) also are made in the bone marrow. White blood cells help fight infection. Platelets stick together to seal small cuts or breaks on the blood vessel walls and stop bleeding. With some types of anemia, you may have low numbers of all three types of blood cells.

Anemia has three main causes: blood loss, lack of red blood cell production, or high rates of red blood cell destruction. These causes may be due to many diseases, conditions, or other factors.

Outlook

Many types of anemia can be mild, short term, and easily treated. You can even prevent some types with a healthy diet. Other types can be treated with dietary supplements.

However, certain types of anemia may be severe, long lasting, and life threatening if not diagnosed and treated.

If you have signs and symptoms of anemia, see your doctor to find out whether you have the condition. Treatment will depend on the cause and severity of the anemia.

Source: National Heart, Lung and Blood Institute

Chromosomes come in pairs. Females have two X chromosomes, while males have one X and one Y chromosome. Only the X chromosome carries the genes related to clotting factors.

A male who has the abnormal gene on his X chromosome will have hemophilia. A female must have the abnormal gene on both of her X chromosomes to have hemophilia; this is very rare.

A female is a “carrier” of hemophilia if she has the abnormal gene on one of her X chromosomes. Even though she doesn’t have the condition, she can pass the gene on to her children.

Below are two examples of how the hemophilia gene is inherited.

Inheritance Pattern for Hemophilia—Example 1

The diagram shows one example of how the hemophilia gene is inherited. In this example, the father doesn’t have hemophilia (that is, he has two normal chromosomes—X and Y). The mother is a carrier of hemophilia (that is, she has one abnormal X chromosome and one normal X chromosome).

Each daughter has a 50 percent chance of inheriting the abnormal gene from her mother and being a carrier. Each son has a 50 percent chance of inheriting the abnormal gene from his mother and having hemophilia.

Inheritance Pattern for Hemophilia—Example 2

The diagram shows another example of how the hemophilia gene is inherited. In this example, the father has hemophilia (that is, his X chromosome is abnormal). The mother isn’t a hemophilia carrier (that is, she has two normal X chromosomes). Each daughter will inherit the abnormal gene from her father and be a carrier. None of the sons will inherit the abnormal gene from their father, and, therefore, none will have hemophilia.

Females who are carriers usually have enough clotting factors from their one normal X chromosome to prevent serious bleeding problems.

Very rarely, a girl is born with hemophilia. This can happen if her father has hemophilia and her mother is a carrier.

Some males who have the disorder are born to mothers who aren’t carriers. In these cases, a mutation (random change) occurs in the gene as it is passed to the child.

Source: NHLBI, NIH

(1) basic mechanisms involved in regulating the production and terminal development of blood cells (hematopoiesis) and in regulating the expression of genes relevant to normal blood cell maturation and function

(2) regulatory molecules, cytokines, and hematopoietic growth factors that influence blood cell production from hematopoietic stem cells and progenitors

(3) blood cell membrane structure and function relevant to the maintenance of blood cell integrity, the tissue localization of hematopoietic progenitor cells, and the circulation and survival of mature blood cells

(4) acquired and congenital disorders of erythrocyte (red blood cell) production (erythropoiesis) and survival including anemias resulting from disturbances in the production or function of hemoglobin (e.g. thalassemias, sickle cell disease)

(5) the molecular biology of heme and hemoglobin synthesis and turnover

(6) the metabolism, storage, and transport of iron and disorders resulting from disturbances in these processes, such as hemochromatosis and iron restricted anemias

(7) the metabolism, structure, and function of leukocytes (white blood cells) and myeloid progenitors

(8) translational applications of new insights and knowledge gained from basic research in these areas towards the development of novel or improved approaches for the diagnosis, stratification, and treatment of hematologic diseases, with a particular emphasis on the development of disease biomarkers, gene targeted therapies, hematopoietic stem cell transplantation in heritable blood diseases, and the measurement and chelation of tissue iron in iron overload disorders.

For more information, contact Dr. Daniel Wright, or Dr. Terry Rogers Bishop, Hematology Program Director.

Source: NHLBI, NIH