CBC, Platelet; No Differential
What is a Complete Blood Count?
A complete blood count (CBC), is a blood test that doctors may use to diagnose certain medical conditions, track the progression of an illness, or determine infection. CBCs measure the different molecules that make up blood and compare them to a scale of normal values for each molecule. The test is performed either in a doctor's office, lab, or hospital and requires a blood sample, often drawn from the arm using a needle. The blood draw itself takes very little time, but the results may take several days depending upon the laboratory used to conduct the analysis.
Blood is made up of three kinds of cells: red blood cells, white blood cells, and platelets. A CBC counts the quantity of each of these types of cells. A machine uses light detectors to analyze a small blood sample and count the number of cells. The cell types are determined by analyzing cell structure, components, and size.
A complete blood count generally analyzes all the components of the blood contained in the red and white cells and the platelets. A white cell count will not only include a total number of white cells but will also look at the different kinds of white cells, which can be broken into five subsets. Neutrophils are the infection fighting white cells and should constitute about half of a white cell count. Low levels of neutrophils may make people more susceptible to infections and may indicate the presence of autoimmune disease. Other types of white blood cells are lymphocytes, basophils, moncytes, and eosinophils.
In a complete blood count, lymphocyte levels may be higher in certain types of infections, including viral infections, or it may indicate leukemia. Monocytes are usually evaluated when a bacterial infection is suspected. Increased eosinophils may indicate a parasitic infection.
Red blood cells are counted and evaluated for their hemoglobin (HGB) value, which carries oxygen from the lungs to the rest of the body. A lower than normal level of hemoglobin may indicate anemia, which can be caused by low iron levels in the blood or by other illnesses. Hematocrit (HCV) is measured as a percentage in relationship to total blood volume and is evaluated in a complete blood count to determine internal bleeding from, for example, traumatic injury during an accident or suspected ectopic pregnancy. HCV levels are routinely checked after surgeries that have resulted in blood loss.
Platelets are evaluated in terms of size and number. Low counts of platelets, called thrombocytenia, can cause excessive bleeding when cut, bruising, and heavier menstrual periods. High counts, called thrombocytosis, indicate a higher risk of stroke due to the formation of blood counts. Taking anti-coagulants often reduces platelet volume, and physicians frequently order a complete blood count to make sure platelet numbers are reducing without becoming dangerously low.
A complete blood count is compared against a normal range. This range is different in children, and there is some degree of difference between the counts of men and women. Corresponding normal ranges are often displayed on CBC reports.
Both the lab and a physician will analyze the complete blood count for anything significantly outside of the range. In fact, patients may not actually see the CBC lab report. However, patients can request to see the report and ask their physicians to explain any anomalies.
What is a Red Blood Cell?
A red blood cell, or erythrocyte, is the most common type of cell in blood. It carries oxygen throughout the circulatory system, from the lungs to the rest of the body, and brings carbon dioxide waste back the other way. All of the body's tissues are dependent upon oxygen from these cells — if the flow is cut off, the tissue dies. There are several medical conditions associated with red blood cells specifically, including sickle-cell anemia, thalassemia, and spherocytosis, but changes in the amount of these cells can also be a sign of other disorders.
Red blood cells have a diameter of about 6 to 8 micrometers (millionths of a meter), which is similar in size to most cells in the body. They are round and red, with a depression in the center. Adult humans have 20 to 30 trillion of these cells in their bodies, with men having more on average than women, and each one lives for about 120 days before being broken down. They are very flexible, which is important for their functioning, since they often have to squeeze through small openings.
The main purpose of red blood cells is to transport oxygen and carbon dioxide through the circulatory system. The reason they can do this is that they contain an iron-containing protein called hemoglobin, which binds to oxygen. When the oxygen and the hemoglobin combine, they cause the cells to become bright red. This is why blood looks red when it goes outside of the body as well — when exposed to the open through a cut, the cells become exposed to a lot of atmospheric oxygen. Once all the oxygen connected to the cells is used up, then they collect carbon dioxide and other waste gases from the body and bring it back to the lungs, where they swap it for oxygen and start the cycle again.
There are a variety of medical disorders associated with red blood cells, with one of the most common being sickle-cell disease. This is a genetic disorder that causes the cells to become stiff and sickle-shaped. This makes them unable to move properly throughout the circulatory system, and can lead to a variety of problems, including strokes, blindness, and chronic pain. Spherocytosis is another genetic condition that changes the shape of cells and makes them brittle, but unlike sickle-cell disease, it makes them spherical.
Several other conditions cause red blood cell abnormalities by disrupting the proper production of hemoglobin. This includes thalassemia, a genetic disorder that causes abnormal hemoglobin molecules, and pernicious anemia, in which the body doesn't absorb enough B12, which is needed for making hemoglobin. Additionally, conditions like G6PD deficiency, hemolytic disease of the fetus and newborn, and aplastic anemia can cause problems with the creation and life of red blood cells.
Besides conditions that affect the cells themselves, having an increase or decrease in the number of red blood cells in the body can be a symptom of several conditions. A high red blood cell count, also called polycythemia, can be caused by poor circulation to the kidneys, genetic heart problems, Chronic Obstructive Pulmonary Disease (COPD), and pulmonary fibrosis. Some people are also born with genetic variants that cause them to have higher than normal red blood cell counts. A lower than normal count can be a sign of poor nutrition, problems with bone marrow, and leukemia, among other things.
What Is Hemoglobin?
Hemoglobin is a protein-based component of red blood cells which is primarily responsible for transferring oxygen from the lungs to the rest of the body. It is actually the reason red blood cells appear red, although oxygen-rich blood is noticeably brighter than the depleted blood returning to the heart and lungs. Fresh hemoglobin is produced in the bone marrow as needed.
The creation of this component is controlled by a complicated genetic code. Because unborn babies obtain their oxygenated blood from their mothers and not their own lungs, two separate substances called hemoglobin alpha and gamma combine with several nitrogen atoms and one iron atom. This allows the fetus to receive oxygen-rich blood without respiration. Once the infant is born, however, the body replaces the gamma with a new variant called hemoglobin beta. The combination of these two substances continues for a lifetime.
Essentially, hemoglobin develops a hunger for oxygen molecules. When the blood is carried into the lungs, the proteins, which contain iron atoms, attract whatever oxygen is available. This oxygenated blood then travels throughout the entire bloodstream, releasing oxygen into the muscles and organs. The spent red blood cells are transferred to the gastrointestinal system for disposal and new red blood cells take their place in the bloodstream.
This ongoing system of hemoglobin proteins obtaining oxygen from the lungs and delivering it to the cells is based on ideal conditions, however. Sometimes the alpha or beta proteins produced by the genetic code are not perfectly formed, as in the case of sickle cell anemia. One of the components is shaped like a sickle, causing an imperfect bond to form.
Anemia means that the red blood cells lack sufficient levels of iron. Without an iron atom, the damaged hemoglobin pigment cannot attract oxygen in the lungs very effectively, if at all. The result can be a slow wasting process leading to complete body dysfunction.
Hemoglobin can also be compromised by blood conditions such as diabetes or cancer. Many standard blood tests included a general check of hemoglobin levels. The amount of glucose in the bloodstream may vary from hour to hour, but an examination of this component often provides a more accurate reading for diabetics.
Another difficulty with hemoglobin is its affinity for gases other than oxygen. It is 200 times more attracted to carbon monoxide than oxygen, for example. This means that someone breathing in carbon monoxide from automobile exhaust could be replacing the oxygen in their lungs with a poison. If enough hemoglobin is exposed to carbon monoxide, the result could be the same as asphyxiation. Cigarette smokers who regularly breath in carbon monoxide could compromise as much as 20% of their total lung oxygen supply.
This attraction to other gases can actually be beneficial under controlled circumstances. It is also attracted to gases used during anesthesia proceedings before surgery. The nitrous oxide or other breathable anesthetic is carried into the brain through the hemoglobin, which allows the surgical team to control the patient's level of consciousness. As oxygen is reintroduced into the patient's lungs, the pigment refreshes itself and the other gases become waste products.
What Is the Hematocrit?
Hematocrit, or HCT, refers to the amount of red blood cells in the entire blood volume. It is measured as a percentage. It is sometimes also referred to as packed cell volume. The hematocrit is measured through a blood test. Abnormal levels can be a sign of various medical illnesses or conditions.
Often an HCT test is ordered as part of a complete blood count. It may be repeated several times to determine if certain conditions, such as anemia, are getting better. The test involves obtaining blood from a vein. A vein, often in the arm or hand, is cleaned with an antiseptic. Next, a needle is inserted into the vein, and the blood is drawn.
Although blood tests are considered routine and rarely result in complications, problems are possible. Infection can develop, especially if the site was not cleaned well before the blood was drawn. Other rare complications that can occur include excessive bleeding and a hematoma at the site.
Once the blood is taken, it is analyzed through special lab equipment to determine the hematocrit. Lab equipment varies and different techniques may be used to get a measurement. Dense blood, containing red blood cells will separate from the liquid component of the blood after being spun in a centrifuge. This helps determine the percentage of the entire volume of blood that contains red blood cells.
Normal levels will differ depending on the patient's gender and age. For instance, in newborns, normal ranges are between 55 and 68 percent. By 10 years of age, 36 to 41 percent is considered normal. The normal male adult values are 42 to 54 percent, and in adult females a normal number is 38 to 46 percent.
A low hematocrit level can indicate various conditions such as excess blood loss, or a nutritional deficiency. Bone marrow diseases, such as leukemia, can also cause a decrease in red blood cells and result in a low hematocrit.
Various conditions may also cause an increased hematocrit. Certain lung diseases, such as chronic obstructive pulmonary disease can cause an increased ratio of red blood cells. Dehydration and being at a high elevation can also often lead to an increased hematocrit.
Another reason to check the HCT may be to check for blood doping among athletes. When an athlete uses steroids, the drugs can increase the percentage of red blood cells in the body and raise the hematocrit above normal levels. A baseline HCT level is often taken on professional athletes to determine what their HCT percentage is. That level is compared to random screenings performed to check for blood doping.
What are Platelets?
Platelets, along with red cells and plasma, form a major proportion of both human and animal blood. Microscopically, they look like little thorned or spiky ovals, and they can only be viewed microscopically, as the average size is about four hundred thousandths of an inch (1 to 3.5 um). Platelets are actually fragments of the cells in bone marrow, called megakaryocytes. Stimulated by the hormone thrombopoietin, platelets break off the megakaryocytes and enter the blood stream, where they circulate for about 10 days before ending their short lives in the spleen. In the healthy body, thrombopoietin will help to maintain the count of platelets at a normal level, which is approximately 4.2-6.1 million of these tiny cells in two hundred thousandths of a teaspoon (1ul) of blood.
Most are familiar with the blood's ability to coagulate should one receive a cut or bruise. Specifically, platelets provide the necessary hormones and proteins for coagulation. Collagen is released when the lining of a blood vessel is damaged. The platelet recognizes collagen and begins to work on coagulating the blood by forming a kind of stopper, so further damage to the blood vessel is prevented.
A higher than normal count of platelets, known as thrombocytosis, can cause serious health risks. Too much clotting of the blood can lead to formation of blood clots that can cause stroke. Conversely, lower than normal counts can lead to extensive bleeding.
However, in some cases, inducing a lower platelet count is desirable, for instance if a person has susceptibility to strokes or has had extensive heart repair. Platelet counts can be lowered by a daily intake of aspirin or other clot reducing drugs. Additionally, when a patient has an intravenous drip (IV), heparin is used to keep the IV from clotting so fluids can be either taken from or added to the body.
While disease or a genetic disorder can cause a lower number of platelets, other times, they are depleted because of a specific treatment or surgery. Burn victims, organ transplant patients, marrow transplant patients, those undergoing chemotherapy, and those who have undergone heart surgery often require not only blood transfusions but platelet transfusions as well.
Almost anyone who is able to donate blood, and is not taking aspirin or other anti-coagulants, is also eligible for platelet donation, called platepheresis or apheresis. In this case, blood is drawn and placed in a centrifuge, where the platelets are separated from the other blood products. The rest of the blood is returned to the body, instead of being collected as it would be in a regular blood donation. The procedure takes from about 90 minutes to two hours.
Once collected, platelets only have a shelf life of about five days, and one donation provides only a sixth of a platelet transfusion unit. Given that bone marrow transplant patients often require up to 120 units of platelets, it is a foregone conclusion that new platelet donations are required daily. Information about platelet donation is available from local blood banks.
What Is Hypereosinophilia?
Hypereosinophilia is a medical term used to describe a rare disorder in which an abnormally high number of eosinophils are present in the bloodstream. Eosinophils are special types of white blood cells which help protect the body from parasitic infections. These blood cells also become active during allergic reactions or as a response to medical conditions such as Cushing's disease. An elevated number of eosinophils in the blood is clinically known as hypereosinophilia and is often detected during routine blood tests. Symptoms of this blood disorder may include swollen lymph nodes, shortness of breath, or the development of a skin rash and should be evaluated and treated by a qualified medical professional.
Eosinophils are an important part of the body's natural immune system and are particularly helpful in helping the body fight infections caused by parasites such as intestinal worms. When a parasitic infection is present, hypereosinophilia develops as a defense mechanism as the immune system is activated in order to fight the invading parasites. When a person experiences an allergic reaction to certain foods, medication, or other substances, it is common for hypereosinophilia to develop. Other illnesses that can lead to an increased production of eosinophils include Cushing's disease, rheumatoid arthritis, and blood cancers such as lymphoma or leukemia.
Mild cases of hypereosinophilia may not cause any noticeable symptoms and are usually only diagnosed if the patient undergoes blood tests for other medical concerns. As the condition progresses, a skin rash may develop or lymph nodes may become swollen and uncomfortable. Respiratory problems such as coughing or wheezing are often experienced by those who have a substantial increase in the number of eosinophils in the blood. If left untreated, hypereosinophilia can lead to complications, such as damage to the heart, liver, or intestines. Blood clots, vision problems, and neurological disturbances are also possible symptoms of this disorder.
Treatment for hypereosinophilia depends upon the underlying cause as well as the presentation of individual symptoms. Cortisone medications are often helpful in alleviating symptoms associated with this condition, although additional medications such as antihistamines or anticoagulants may be needed in some situations. More invasive treatment methods, including surgery or organ transplantation, are sometimes required when there has been significant tissue damage that affects the proper functioning of the organ concerned. It is important to follow the advice of the supervising physician any time that hypereosinophilia is diagnosed, and any new or bothersome symptoms should be reported for further evaluation and treatment.
What Causes a Low Lymphocyte Count?
There are several possible causes for a low lymphocyte count, including disease processes and the use of certain medications. Infectious diseases, autoimmune disorders, and some forms of cancer frequently lead to this symptom. The use of steroid medications is sometimes responsible for the development of a low lymphocyte count. Treatment is focused on proper medical management of the underlying cause of the reduced lymphocyte count. Any specific questions concerning an individual experience with a low lymphocyte count should be discussed with a doctor or other medical professional.
In many cases, a low lymphocyte count is due to the presence of an infectious disease. Some of the specific diseases that are known to lead to this symptom include AIDS, tuberculosis, and viral hepatitis. Acquired immunodeficiency syndrome, more commonly known as AIDS, is a severe complication of a virus known as HIV that causes destruction of the patient's immune system. Tuberculosis is a bacterial infection that primarily affects the lungs and can be fatal if not properly treated. Viral hepatitis is a form of liver disease that can lead to cancer of the liver, especially if left untreated.
A variety of autoimmune disorders can cause a low lymphocyte count, including lupus, multiple sclerosis, and rheumatoid arthritis. Lupus causes inflammation in various organs of the body and can be fatal in the most severe instances. Multiple sclerosis is a disease that destroys the protective covering of the nerves and can cause varying degrees of physical disability. Rheumatoid arthritis leads to chronic inflammation of the joints and may cause pain and joint deformities.
Cancer, especially forms of cancer that affect the blood, are possible causes of a low lymphocyte count. Leukemia and lymphoma are commonly associated with this symptom. Chemotherapy and radiation therapy are the standard treatment options for these cancers, and the treatments themselves can cause the lymphocyte count to drop even further. Steroid medications are used to treat several types of inflammatory conditions and may cause a temporary decline in the number of lymphocytes in the blood.
The majority of cases involving a low lymphocyte count are not serious and can be successfully treated with antibiotics or other medications. Simple blood tests can detect this condition, often leading to additional testing in order to determine the underlying cause. In many situations, there are no noticeable symptoms, so regular check-ups with a doctor can help to detect any potential problems before serious complications develop.
What Is the Connection Between Hemoglobin and Hematocrit?
Hemoglobin and hematocrit are two important components of the complete blood count, a test that a doctor might order to determine whether there are any abnormalities in a patient's blood chemistry. Both "hemoglobin" and "hematocrit" refer to specific characteristics of red blood cells, but they measure different things. Hemoglobin is an oxygen-binding compound that transports oxygen to the cells, and the hemoglobin test measures how much of this compound is present. The hematocrit test determines how much of the total blood volume contains red blood cells.
Doctors request hemoglobin and hematocrit together along with other measurements of blood chemistry to get a complete picture of a patient's blood chemistry and general level of health. Some things can skew the measures. A severely dehydrated or fluid-loaded patient will have abnormal blood volume as a result of variations in the level of blood plasma, for instance. Dehydrated patients might have an unusually high hematocrit level because there are more red blood cells as a total percentage of blood volume.
Normal hemoglobin levels for women range from 12-16 grams per decaliter, and men have slightly higher values, 14-18. If the levels are low, it can indicate that a patient has anemia. Lack of hemoglobin means that the patient's body will not get enough oxygen. This can lead to the development of fatigue and other issues, including organ failure, slow wound healing and secondary complications. Patients can also have too much hemoglobin, as seen in conditions such as polycythemia vera.
Red blood cells are basically vessels for hemoglobin, so there is a very direct relationship between hemoglobin and hematocrit. Patients who have low levels of red blood cells might have low hemoglobin levels because their bodies don't have enough red blood cells to meet their needs. Likewise, high levels can lead to an excess of this compound. Patients who are in need of transfusion to replace lost blood or compensate for low blood cell production might receive a hemoglobin and hematocrit test to determine their baseline levels and to see how well they respond to transfusion.
Hematocrit values can range from 40-54 percent in men and 36-48 percent in women. With a hemoglobin and hematocrit test, the doctor will want to know whether the patient is on any medications or has ingested unusually high or low levels of fluid. If the values appear to be abnormal, these might be considered as factors before exploring possible diseases that might cause a high or low concentration of red blood cells.
What Can Doctors Learn from a Complete Blood Count?
One of the most common tests that doctors order is a complete blood count (CBC), in which blood is drawn from a vein in the patient's arm. Some doctors order a blood panel during a routine checkup, while others only do so when patients complain of symptoms, such as fatigue or excessive bleeding. This is because this type of screening allows doctors to diagnose various conditions, including infections, diseases and side effects of medications. Doctors tend to pay a lot of attention to both the white and red blood cell counts. They also can use the complete blood count results to find out more about the platelets and hemoglobin in the patient.
White blood cells are considered an important aspect of a complete blood count, because an abnormal number of these shows that the body is likely fighting an infection. Therefore, a full blood exam counts the number of white blood cells and also considers the types that are present, which is done by analyzing the size and shape of each cell. Doctors can usually spot an infection after looking at the information gathered about the white blood cells during a complete blood count. They also can determine the side effects of certain medications on the body, because some drugs cause an abnormal number of white blood cells.
Another aspect of a full blood count to which doctors pay attention is red blood cells. A CBC counts the number of red blood cells, and analyzes both the size of these cells and variations in the size. In addition, a CBC measures the amount of hemoglobin in red blood cells, because this substance is meant to help distribute oxygen to the entire body. A low level of hemoglobin can lead to anemia, which often causes patients to feel constantly tired and bruise easily. Therefore, patients complaining of these symptoms are often given a CBC so their doctor can diagnose and treat them as soon as possible.
Platelets also are measured during a complete blood count, because they are important in stopping bleeding. Thus, patients who notice excessive bleeding without clotting may have to get a blood panel so their doctor can diagnose and treat the issue. This kind of test not only analyzes the number of platelets, but also the size, because smaller platelets are generally older. Therefore, results that show mostly small platelets may indicate reduced production of this cell, signaling a problem.
What Are Abnormal Lab Values?
Any time a person has laboratory work done, whether it involves blood tests, a urinalysis, or some other type of testing, the results of the testing are compared with results that are considered normal for the group that person falls into, usually determined by the person’s age and gender. The numbers used as a basis for comparison are the result of large numbers of tests done on healthy people over a period of years. If a person’s test results fall outside of the parameters of what is considered normal, the person is said to have abnormal lab values.
Because there is no one right answer for what a person’s tests should be, it is possible for an individual to have abnormal lab values and still be at an acceptable level. This determination is made by the person’s doctor and takes into account how far outside the normal range the lab values are, which results are in question, and the health status of the person being tested. Often testing can reveal abnormal lab values that are the first clue to hidden problems in a person who feels fine.
Sometimes, abnormal lab values indicate a need for further testing, such as when a person’s laboratory readings indicate a possible problem with the liver, heart, or kidneys. Other times, abnormal lab values are a clue that the person needs to make an important lifestyle change, such as when there are high cholesterol or triglyceride vales. Making changes to diet and exercise can help bring values that are outside of the normal range back into the range of what are considered acceptable numbers.
The specific laboratory tests used on a person generally depend on what the physician is looking for. Not all tests are ordered in all situations. Some of the more common tests, usually used as broad indicators of a person’s health, are tests for cholesterol, triglycerides, hemoglobin, platelet count, red blood cells, and white blood cells. Abnormal lab values in any of these areas can signify potentially serious problems and require further investigation.
In some cases, such as for people over a certain age, very specific tests are ordered to look for signs that might indicate cancer, thyroid problems, heart trouble, liver problems, or anemia. If abnormal lab values are found in any of these areas, a more thorough investigation is usually begun immediately, as poor lab test results can sometimes indicate the impending failure of an organ or the presence of cancer. X-rays and other imaging tests typically follow up indications of organ problems, with the ultimate hope of resolving any problems before they become too serious, thus restoring normal function to the body.
What Is Mean Corpuscular HGB?
The mean corpuscular hemoglobin (hgb) is a laboratory study that is performed to evaluate the red blood cells. It is one of the many results reported as part of the complete blood count, which is a commonly done lab test. Evaluating the amount of hemoglobin present in red blood cells is important because hemoglobin is responsible for carrying oxygen throughout the body. Low mean corpuscular hemoglobin levels reflect a condition called microcytosis, whereas high levels correlate to macrocytosis.
Mean corpuscular hgb, also known as the mean cellular hgb, is often abbreviated as MCH. It is a measure of the average hemoglobin concentration present in a red blood cell. MCH is reported as part of a complete blood count (CBC), which is a study that measures the number of white blood cells, red blood cells, and platelets present in the blood. The CBC gives a significant amount of information regarding the red blood cells, including the concentration of hemoglobin in the blood, the MCH, the mean corpuscular hemoglobin concentration (MCHC), the mean corpuscular volume (MCV), and red cell distribution width (RDW).
In order to understand why measuring the mean corpuscular hgb is important, it helps to understand the role that hemoglobin plays in the physiology of the body. Hemoglobin is a protein located within red blood cells, and it is responsible for carrying oxygen. Typically this protein picks up oxygen molecules in the lungs, carries the oxygen to distant parts of the body, and drops it off for these cells to use as part of their metabolic processes. Without enough hemoglobin circulating in the blood, insufficient amounts of oxygen will be distributed throughout the body.
The mean corpuscular hgb is usually low in a condition called microcytosis, which occurs when the red blood cells are smaller than would be expected. As the cells themselves are small, their average amount of hemoglobin is low. A number of medical conditions can cause microcytosis. Iron deficiency anemia, which is having low numbers of red blood cells due to a lack of iron in the body, is the most common cause. Another cause of microcytosis is thalassemia, which is a genetic disease that makes the body produce abnormal hemoglobin.
On the other end of the spectrum, having a high mean corpuscular hgb is associated with macrocytosis. This condition occurs when the red blood cells are larger than they should be. One common cause of macrocytosis is megaloblastic anemia, which is having a low red blood cell count due to dietary deficiencies in vitamins such as folate or vitamin B12. Macrocytosis can also occur when the body is actively trying to make new red blood cells, and precursor cells called reticulocytes enter the body’s circulation. These reticulocytes are larger than mature red blood cells.
Complete Blood Count Test
What is a complete blood count?
A complete blood count (CBC) is a blood test that is commonly ordered by doctors. A CBC is often ordered as part of a complete physical or when your doctor thinks you might have a certain condition, such as an infection. A CBC may also be done to check on levels of prescribed medications in the body.
The test (which actually consists of several tests) gives details about three types of blood cells: red blood cells, white blood cells, and platelets. The CBC reports how many cells there are in the blood, and the physical characteristics of the cells, such as size, shape, and content.
How is a complete blood count test performed?
In order to perform the CBC panel of tests, blood must be drawn from the patient. In adults, the blood is usually obtained from a vein in the arm. In infants, the blood is usually taken from the heel.
What should I do to prepare for a complete blood count test?
You do not have to do anything to prepare for a CBC.
What is a red blood cell, and what does a red blood cell count tell?
Red blood cells are the part of the blood that carry oxygen and carbon dioxide throughout the body. Red blood cells are made up of hemoglobin, which contains iron as part of its structure. The amount of oxygen that is combined with hemoglobin helps give the cells their red color. The hemoglobin carries oxygen to tissues and carbon dioxide (waste) away from tissues. The carbon dioxide leaves the body when it is exhaled through the lungs. Red blood cells are measured in millions per cubic millimeter (mil/mm3) of blood.
What is a white blood cell, and what does a white blood cell count tell?
White blood cells are the part of the blood that fight infections. White blood cells are measured in thousands per cubic milliliter (K/ml3) of blood.
A further test (white blood cell differential) might be done at the same time as the other blood tests. This test classifies the different kinds of white blood cells, which all have different jobs in keeping us healthy. The cells are: neutrophils (also called segs, PMNs, granulocytes, or grans), lymphocytes, monocytes, eosinophils, and basophils.
What other measurements are shown by a complete blood count?
Hematocrit (HCT)—the percentage of red blood cells in the total volume of blood
Platelet count—the number of platelets in thousands per cubic milliliter (K/ml3) of blood. Platelets form clots in order to stop bleeding.
Mean platelet volume (MPV)—the average size of platelets. This is important because new platelets are bigger than older ones, and a higher MPV indicates a higher platelet output.
Mean corpuscular hemoglobin (MCH)—the average amount of hemoglobin in a red blood cell.
Mean corpuscular hemoglobin concentration (MCHC)—the average concentration of hemoglobin in a red blood cell. The MCHC gives the health care provider an impression of the pallor of the cell; for example, very pale to very dark red. The degree of paleness may help in establishing a diagnosis.
Mean corpuscular volume (MCV)—the average size of red blood cells. "Macrocytic" describes a state in which red blood cells are bigger than normal; "microcytic" refers to the state in which red blood cells are smaller than normal. The average size of the red blood cells may help in establishing a diagnosis.
Red blood cell distribution width (RDW)—the amount of variation in the size of the red blood cells.
Blood counts may vary with altitude. In general, normal results are:
Male: 4.7 to 6.1 million cells/mcL
Female: 4.2 to 5.4 million cells/mcL
Male: 40.7 to 50.3%
Female: 36.1 to 44.3%
Male: 13.8 to 17.2 gm/dL
Female: 12.1 to 15.1 gm/dL
Red blood cell indices:
MCV: 80 to 95 femtoliter
MCH: 27 to 31 pg/cell
MCHC: 32 to 36 gm/dL
Platelet (thrombocyte) count
Adults: 140,000-400,000 platelets per mm3 or 140-400 x 109/L
Children: 150,000-450,000 platelets per mm 3 or 150-450 x 109/L
cells/mcL = cells per microliter
gm/dL = grams per deciliter;
pg/cell = picograms per cell
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What kinds of disorders can be detected with a complete blood count?
Doctors may order a CBC when the patient has signs of infection, is weak or tired, or has inflammation (swelling), bruising, or bleeding. Some of these conditions may require treatment, while others may disappear on their own. Blood counts may also be affected by various medications and dietary deficiencies.
Abnormal CBC results help to diagnose:
- Autoimmune conditions (diseases in which the body’s immune system attacks the body)
- Bone marrow failure
- Abnormal development of bone marrow
- Dehydration, fluid loss
- Vitamin and mineral deficiencies
- Thalassemia (a blood disorder in which the production of red blood cells is abnormal)
- Effects of chemotherapy
- Effects of certain antibiotics
- Effects of a number of medications in long-term or even short-term use.