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Complete blood count

Complete blood count

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A complete blood count (CBC), also known as full blood count (FBC) or full blood exam (FBE) or blood panel, is a test panel
Test panel
A test panel is a predetermined group of medical tests as an aid in the diagnosis and treatment of disease.Test panels are typically composed of individual laboratory tests which are related in some way: by the medical condition they are intended to help diagnose , by the specimen type , by the...

 requested by a doctor
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 or other medical professional that gives information about the cells in a patient's blood. A scientist or lab technician performs the requested testing and provides the requesting medical professional with the results of the CBC.

Alexander Vastem is widely regarded as being the first person to use the complete blood count for clinical purposes. Reference ranges used today stem from his clinical trials in the early 1960s.

The cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 that circulate in the blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

stream are generally divided into three types: white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes). Abnormally high or low counts may indicate the presence of many forms of disease, and hence blood counts are amongst the most commonly performed blood test
Blood test
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....

s in medicine, as they can provide an overview of a patient's general health status. A CBC is routinely performed during annual physical examination
Physical examination
Physical examination or clinical examination is the process by which a doctor investigates the body of a patient for signs of disease. It generally follows the taking of the medical history — an account of the symptoms as experienced by the patient...

s in some jurisdictions.

Samples



A phlebotomist
Phlebotomist
Phlebotomists are individuals trained to draw blood from a live person or animal.Phlebotomists collect blood primarily by performing venipuncture and, for collection of minute quantities of blood, fingersticks. Blood may be collected from infants by means of a heel stick...

 collects the sample, drawing the blood into a test tube
Test tube
A test tube, also known as a culture tube or sample tube, is a common piece of laboratory glassware consisting of a finger-like length of glass or clear plastic tubing, open at the top, usually with a rounded U-shaped bottom....

 containing an anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

 (EDTA
EDTA
Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...

, sometimes citrate
Citrate
A citrate can refer either to the conjugate base of citric acid, , or to the esters of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate.-Other citric acid ions:...

) to stop it from clotting
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

. The sample is then transported to a laboratory
Laboratory
A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...

.

In the past, counting the cells in a patient's blood was performed manually, by viewing a slide prepared with a sample of the patient's blood under a microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

 (a blood film
Blood film
A blood film or peripheral blood smear is a thin layer of blood smeared on a microscope slide and then stained in such a way to allow the various blood cells to be examined microscopically...

, or peripheral smear). Nowadays, this process is generally automated by use of an automated analyzer, with only approximately 30% of samples now being examined manually.

Automated blood count



The blood is well mixed (though not shaken) and placed on a rack in the analyzer. This instrument has many different components to analyze different elements in the blood. The cell counting component counts the numbers and types of different cells within the blood. The results are printed out or sent to a computer for review.

Blood counting machines aspirate a very small amount of the specimen through narrow tubing. Sensors count the number of cells passing through the tubing, and can identify the type of cell; this is flow cytometry
Flow cytometry
Flow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...

. The two main sensors used are light detectors and electrical impedance
Electrical impedance
Electrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...

. One way the instrument can tell what type of blood cell is present is by size. Other instruments measure different characteristics of the cells to categorize them.

Because an automated cell counter samples and counts so many cells, the results are very precise. However, certain abnormal cells in the blood may not be identified correctly, requiring manual review of the instrument's results and identification of any abnormal cells the instrument could not categorize.

In addition to counting, measuring and analyzing red blood cells, white blood cells and platelets, automated hematology analyzers also measure the amount of hemoglobin in the blood and within each red blood cell. This information can be very helpful to a physician who, for example, is trying to identify the cause of a patient's anemia. If the red cells are smaller or larger than normal, or if there is a lot of variation in the size of the red cells, this data can help guide the direction of further testing and expedite the diagnostic process so patients can get the treatment they need quickly.

Manual blood count


Counting chambers that hold a specified volume of diluted blood (as there are far too many cells if it is not diluted) are used to calculate the number of red and white cells per litre of blood.

To identify the numbers of different white cells, a blood film
Blood film
A blood film or peripheral blood smear is a thin layer of blood smeared on a microscope slide and then stained in such a way to allow the various blood cells to be examined microscopically...

 is made, and a large number of white cells (at least 100) are counted. This gives the percentage of cells that are of each type. By multiplying the percentage with the total number of white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...

s, the absolute number of each type of white cell can be obtained.

Manual counting is useful in cases where automated analyzers cannot reliably count abnormal cells, such as those cells that are not present in normal patients and are only seen in peripheral blood with certain haematological conditions. Manual counting is subject to sampling error because so few cells are counted compared with automated analysis.

Medical technicians examine blood film via a microscope for 30% of CBCs, not only to find abnormal white cells, but also because variation in the shape of red cells is an important diagnostic tool. Although automated analysers give fast, reliable results regarding the number, average size, and variation in size of red blood cells, they do not detect cells' shapes. Also, some normal patients' platelets will clump in EDTA anticoagulated blood, which causes automatic analysers to give a falsely low platelet count. The technician viewing the slide in these cases will see clumps of platelets and can estimate if there are low, normal, or high numbers of platelets.

Results


For examples of standard values, see Reference ranges for blood tests#Hematology.

A complete blood count will normally include:

Red cells

  • Total red blood cell
    Red blood cell
    Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

    s — The number of red cells is given as an absolute number per litre.
  • Hemoglobin
    Hemoglobin
    Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...

     - The amount of hemoglobin in the blood, expressed in grams per decilitre. (Low hemoglobin is called anemia
    Anemia
    Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

    .)
  • Hematocrit
    Hematocrit
    The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...

     or packed cell volume (PCV) - This is the fraction of whole blood volume that consists of red blood cells.
  • Red blood cell indices
    Red blood cell indices
    Red blood cell indices are blood tests that provide information about the hemoglobin content and size of red blood cells. Abnormal values indicate the presence of anemia and which type of anemia it is.- Mean corpuscular volume :...

    • Mean corpuscular volume
      Mean corpuscular volume
      The mean corpuscular volume, or "mean cell volume" , is a measure of the average red blood cell size that is reported as part of a standard complete blood count....

       (MCV) - the average volume of the red cells, measured in femtolitre
      Femtolitre
      The femto litre is the metric unit of volume equal to 10−15 litre, or one quinine cillionth or one quadrillionth litre. It is abbreviated FL or fl. One femto litre is the same as 1 μm3.1....

      s. Anemia
      Anemia
      Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

       is classified as microcytic
      Microcytic anemia
      Microcytic anemia is a generic term for any type of anemia characterized by small red blood cells. The normal mean corpuscular volume is 76-100 fL, with smaller cells as macrocytic....

       or macrocytic based on whether this value is above or below the expected normal range. Other conditions that can affect MCV include thalassemia
      Thalassemia
      Thalassemia is an inherited autosomal recessive blood disease that originated in the Mediterranean region. In thalassemia the genetic defect, which could be either mutation or deletion, results in reduced rate of synthesis or no synthesis of one of the globin chains that make up hemoglobin...

      , reticulocytosis
      Reticulocytosis
      Reticulocytosis is a condition where there is an increase in reticulocytes, immature red blood cell.It is commonly seen in Anemia. They are seen on blood films when the bone marrow is highly active in an attempt to replace red blood cell loss such as in haemolytic anaemia, haemorrhage.-External...

       and alcoholism
      Alcoholism
      Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...

      .
    • Mean corpuscular hemoglobin
      Mean corpuscular hemoglobin
      The mean corpuscular hemoglobin, or "mean cell hemoglobin" , is the average mass of hemoglobin per red blood cell in a sample of blood. It is reported as part of a standard complete blood count...

       (MCH) - the average amount of hemoglobin per red blood cell, in picograms.
    • Mean corpuscular hemoglobin concentration
      Mean corpuscular hemoglobin concentration
      The mean corpuscular hemoglobin concentration, or MCHC, is a measure of the concentration of hemoglobin in a given volume of packed red blood cells. It is reported as part of a standard complete blood count....

       (MCHC) - the average concentration of hemoglobin in the cells.
    • Red blood cell distribution width
      Red blood cell distribution width
      The red blood cell distribution width is a measure of the variation of red blood cell width that is reported as part of a standard complete blood count. Usually red blood cells are a standard size of about 6–8 μm. Certain disorders, however, cause a significant variation in cell size. Higher...

       (RDW) - the variation in cellular volume of the RBC population.

White cells

  • Total white blood cells — All the white cell types are given as a percentage and as an absolute number per litre.


A complete blood count with differential will also include:
  • Neutrophil granulocyte
    Neutrophil granulocyte
    Neutrophil granulocytes are the most abundant type of white blood cells in mammals and form an essential part of the innate immune system. They are generally referred to as either neutrophils or polymorphonuclear neutrophils , and are subdivided into segmented neutrophils and banded neutrophils...

    s — May indicate bacteria
    Bacteria
    Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

    l infection. May also be raised in acute viral infections. Because of the segmented appearance of the nucleus, neutrophils are sometimes referred to as "segs." The nucleus of less mature neutrophils is not segmented, but has a band or rod-like shape. Less mature neutrophils — those that have recently been released from the bone marrow into the bloodstream — are known as "bands" or "stabs". Stab is a German term for rod.
  • Lymphocyte
    Lymphocyte
    A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...

    s — Higher with some viral
    Virus
    A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

     infections such as glandular fever and. Also raised in chronic lymphocytic leukemia
    Chronic lymphocytic leukemia
    B-cell chronic lymphocytic leukemia , also known as chronic lymphoid leukemia , is the most common type of leukemia. Leukemias are cancers of the white blood cells . CLL affects B cell lymphocytes. B cells originate in the bone marrow, develop in the lymph nodes, and normally fight infection by...

     (CLL). Can be decreased by HIV infection. In adults, lymphocytes are the second most common WBC type after neutrophils. In young children under age 8, lymphocytes are more common than neutrophils.
  • Monocyte
    Monocyte
    Monocytes are a type of white blood cell and are part of the innate immune system of vertebrates including all mammals , birds, reptiles, and fish. Monocytes play multiple roles in immune function...

    s — May be raised in bacterial infection, tuberculosis, malaria, Rocky Mountain spotted fever, monocytic leukemia, chronic ulcerative colitis and regional enteritis
  • Eosinophil granulocyte
    Eosinophil granulocyte
    Eosinophil granulocytes, usually called eosinophils or eosinophiles , are white blood cells that are one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along with mast cells, they also control mechanisms associated with...

    s — Increased in parasitic infections, asthma, or allergic reaction.
  • Basophil granulocyte
    Basophil granulocyte
    Basophil granulocytes, sometimes referred to as basophils, are the least common of the granulocytes, representing about 0.01% to 0.3% of circulating white blood cells....

    s — May be increased in bone marrow related conditions such as leukemia or lymphoma.


A manual count will also give information about other cells that are not normally present in peripheral blood, but may be released in certain disease processes.

Platelets

  • Platelet
    Platelet
    Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days...

     numbers are given, as well as information about their size and the range of sizes in the blood.
  • Mean platelet volume
    Mean platelet volume
    Mean platelet volume is a machine-calculated measurement of the average size of platelets found in blood and is typically included in blood tests as part of the CBC...

     (MPV) - a measurement of the average size of platelets.

Interpretation


Certain disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

 states are defined by an absolute increase or decrease in the number of a particular type of cell in the bloodstream. For example:
Type of Cell Increase >-
| Red Blood Cells
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

(RBC)
erythrocytosis or polycythemia
Polycythemia
Polycythemia is a disease state in which the proportion of blood volume that is occupied by red blood cells increases...

 
anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

 or erythroblastopenia
>-
| White Blood Cells
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...

(WBC):
leukocytosis
Leukocytosis
Leukocytosis is a raised white blood cell count above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, and is observed in certain parasitic infections...

 
leukopenia
Leukopenia
Leukopenia is a decrease in the number of white blood cells found in the blood, which places individuals at increased risk of infection....


>-
| -- lymphocyte
Lymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...

s
-- lymphocytosis
Lymphocytosis
Lymphocytosis is an increase in the number or proportion of lymphocytes in the blood, usually detected when a complete blood count is routinely obtained. Lymphocytes normally represent 20 to 40% of circulating white blood cells...

 
lymphocytopenia
Lymphocytopenia
Lymphocytopenia, or lymphopenia, is the condition of having an abnormally low level of lymphocytes in the blood. Lymphocytes are a white blood cell with important functions in the immune system...


>-
| -- granulocyte
Granulocyte
Granulocytes are a category of white blood cells characterized by the presence of granules in their cytoplasm. They are also called polymorphonuclear leukocytes because of the varying shapes of the nucleus, which is usually lobed into three segments...

s:
-- granulocytosis
Granulocytosis
In medicine, granulocytosis is the presence in peripheral blood of an increased number of granulocytes, a category of white blood cells. Often, the word refers to an increased neutrophil granulocyte count, as neutrophils are the main granulocytes.-Causes:...

 
agranulocytosis
Agranulocytosis
Granulopenia, also known as Agranulosis or Agranulocytosis, is an acute condition involving a severe and dangerous leukopenia , most commonly of neutrophils causing a neutropenia in the circulating blood. It represents a severe lack of one major class of infection-fighting white blood cells...


>-
| -- --neutrophils
Neutrophil granulocyte
Neutrophil granulocytes are the most abundant type of white blood cells in mammals and form an essential part of the innate immune system. They are generally referred to as either neutrophils or polymorphonuclear neutrophils , and are subdivided into segmented neutrophils and banded neutrophils...

 
-- --neutrophilia
Neutrophilia
Neutrophilia is a condition where a person has a high number of neutrophil granulocytes in their blood.-Causes:...

 
neutropenia
Neutropenia
Neutropenia, from Latin prefix neutro- and Greek suffix -πενία , is a granulocyte disorder characterized by an abnormally low number of neutrophils, the most important type of white blood cell...


>-
| -- --eosinophils
Eosinophil granulocyte
Eosinophil granulocytes, usually called eosinophils or eosinophiles , are white blood cells that are one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along with mast cells, they also control mechanisms associated with...

 
-- --eosinophilia
Eosinophilia
Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds 0.45×109/L . A marked increase in non-blood tissue eosinophil count noticed upon histopathologic examination is diagnostic for tissue eosinophilia. Several causes are known, with the most common being...

 
eosinopenia
Eosinopenia
Eosinopenia is a form of agranulocytosis where the number of eosinophil granulocyte is lower than expected.Leukocytosis with eosinopenia can be a predictor of bacterial infection....


>-
| -- --basophils
Basophil granulocyte
Basophil granulocytes, sometimes referred to as basophils, are the least common of the granulocytes, representing about 0.01% to 0.3% of circulating white blood cells....

 
-- --basophilia
Basophilia
Basophilia is a condition where the basophil quantity is abnormally elevated .-Causes:Basophilia as an isolated finding is uncommon. However it is a common feature of myeloproliferative disorders and particularly prominent in chronic myelogenous leukemia....

 
basopenia
Basopenia
Basopenia is a form of agranulocytosis associated with a deficiency of basophils.One cause is urticaria.It has been proposed as an indicator of ovulation....


>-
| Platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days...

s
thrombocytosis
Thrombocytosis
Thrombocytosis is the presence of high platelet counts in the blood, and can be either primary or reactive...

 
thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...


>-
| All cell lines
- pancytopenia
Pancytopenia
Pancytopenia is a medical condition in which there is a reduction in the number of red and white blood cells, as well as platelets.If only two parameters from the full blood count are low, the term bicytopenia can be used...



Many disease states are heralded by changes in the blood count:
  • leukocytosis
    Leukocytosis
    Leukocytosis is a raised white blood cell count above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, and is observed in certain parasitic infections...

     can be a sign of infection.
  • thrombocytopenia
    Thrombocytopenia
    Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...

     can result from drug toxicity.
  • pancytopenia
    Pancytopenia
    Pancytopenia is a medical condition in which there is a reduction in the number of red and white blood cells, as well as platelets.If only two parameters from the full blood count are low, the term bicytopenia can be used...

     is generally referred to as the result of decreased production from the bone marrow
    Bone marrow
    Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

    , and is a common complication of cancer
    Cancer
    Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

     chemotherapy
    Chemotherapy
    Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....

    .

External links

  • Blood Groups and Red Cell Antigens. Free online book at NCBI
    National Center for Biotechnology Information
    The National Center for Biotechnology Information is part of the United States National Library of Medicine , a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper...

    Bookshelf ID: NBK2261
  • Complete Blood Count