blood count

Blood Count

Definition

One of the most commonly ordered clinical laboratory tests, a blood count, also called a complete blood count (CBC), is a basic evaluation of the cells (red blood cells, white blood cells, and platelets) suspended in the liquid part of the blood (plasma). It involves determining the numbers, concentrations, and conditions of the different types of blood cells.

Purpose

The CBC is a useful screening and diagnostic test that is often done as part of a routine physical examination. It can provide valuable information about the blood and blood-forming tissues (especially the bone marrow), as well as other body systems. Abnormal results can indicate the presence of a variety of conditions—including anemias, leukemias, and infections—sometimes before the patient experiences symptoms of the disease.

Description

A complete blood count is actually a series of tests in which the numbers of red blood cells, white blood cells, and platelets in a given volume of blood are counted. The CBC also measures the hemoglobin content and the packed cell volume (hematocrit) of the red blood cells, assesses the size and shape of the red blood cells, and determines the types and percentages of white blood cells. Components of the complete blood count (hemoglobin, hematocrit, white blood cells, platelets, etc.) can also be tested separately, and are sometimes done that way when a doctor wants to monitor a specific condition, such as the white cell count of a patient diagnosed with leukemia, or the hemoglobin of a patient who has recently received a blood transfusion. Because of its value, though, as an indicator of a person's overall health, the CBC package is most frequently ordered.The blood count is performed relatively inexpensively and quickly. Most laboratories routinely use some type of automated equipment to dilute the blood, sample a measured volume of the diluted suspension, and count the cells in that volume. In addition to counting actual numbers of red cells, white cells, and platelets, the automated cell counters also measure the hemoglobin and calculate the hematocrit and the red blood cell indices (measures of the size and hemoglobin content of the red blood cells). Technologists then examine a stained blood smear under the microscope to identify any abnormalities in the appearance of the red blood cells and to report the types and percentages of white blood cells observed.The red blood cell (RBC) count determines the total number of red cells (erythrocytes) in a sample of blood. The red cells, the most numerous of the cellular elements, carry oxygen from the lungs to the body's tissues. Hemoglobin (Hgb) is the protein-iron compound in the red blood cells that enables them to transport oxygen. Its concentration corresponds closely to the RBC count. Also closely tied to the RBC and hemoglobin values is the hematocrit (Hct), which measures the percentage of red blood cells in the total blood volume. The hematocrit (expressed as percentage points) is normally about three times the hemoglobin concentration (reported as grams per deciliter).Red blood cell indices provide information about the size and hemoglobin content of the red cells. They are useful in differentiating types of anemias. The indices include four measurements that are calculated using the RBC count, hemoglobin, and hematocrit results. Mean corpuscular volume (MCV) is a measurement of the average size of the red blood cells and indicates whether that is small, large or normal. The red blood cell distribution width (RDW) is an indication of the variation in RBC size. Mean corpuscular hemoglobin (MCH) measures the average amount (weight) of hemoglobin within a red blood cell. A similar measurement, mean corpuscular hemoglobin concentration (MCHC), expresses the average concentration of hemoglobin in the red blood cells.The white blood cell (WBC) count determines the total number of white cells (leukocytes) in the blood sample. Fewer in number than the red cells, WBCs are the body's primary means of fighting infection. There are five main types of white cells (neutrophils, lymphocytes, monocytes, eosinophils, and basophils), each of which plays a different role in responding to the presence of foreign organisms in the body. A differential white cell count is done by staining a smear of the patient's blood with a Wright's stain, allowing the different types of white cells to be clearly seen under the microscope. A technologist then counts a minimum of 100 WBCs and reports each type of white cell as a percentage of the total white blood cells counted.The platelet count is an actual count of the number of platelets (thrombocytes) in a given volume of blood. Platelets, the smallest of the cellular elements of blood, are involved in blood clotting. Because platelets can clump together, the automated counting method is subject to a certain level of error and may not be accurate enough for low platelet counts. For this reason, very low platelet levels are often counted manually.

Normal results

Blood count values can vary by age and sex. The normal red blood cell count ranges from 4.2-5.4 million RBCs per microliter of blood for men and 3.6-5.0 million for women. Hemoglobin values range from 14-18 grams per deciliter of blood for men and 12-16 grams for women. The normal hematocrit is 42-54% for men and 36-48% for women. The normal number of white blood cells for both men and women is approximately 4,000-10,000 WBCs per microliter of blood.

Abnormal results

Abnormal blood count results are seen in a variety of conditions. One of the most common is anemias, which are characterized by low RBC counts, hemoglobins, and hematocrits. Infections and leukemias are associated with increased numbers of WBCs.

Resources

Books

Berkow, Robert, ed. Merck Manual of Medical Information. Whitehouse Station, NJ: Merck Research Laboratories, 1997.Henry, J. B. Clinical Diagnosis and Management by Laboratory Methods. New York: W. B. Saunders Co., 1996.

blood

[blud] the fluid that circulates through the heart, arteries, capillaries, and veins and is the chief means of transport within the body. It transports oxygen from the lungs to the body tissues, and carbon dioxide from the tissues to the lungs. It transports nutritive substances and metabolites to the tissues and removes waste products to the kidneys and other organs of excretion. It has an essential role in the maintenance of fluid balance.
In an emergency, blood cells and antibodies carried in the blood are brought to a point of infection, or blood-clotting substances are carried to a break in a blood vessel. The blood distributes hormones from the endocrine glands to the organs they influence. It also helps regulate body temperature by carrying excess heat from the interior of the body to the surface layers of the skin, where the heat is dissipated to the surrounding air.
Blood varies in color from a bright red in the arteries to a duller red in the veins. The total quantity of blood within an individual depends upon body weight; a person weighing 70 kg (154 lb) has about 4.5 liters of blood in the body.
Blood is composed of two parts: the fluid portion is called plasma" >plasma, and the solid portion or formed elements (suspended in the fluid) consists of the blood cells (erythrocytes and leukocytes) and the platelets. Plasma accounts for about 55 per cent of the volume and the formed elements account for about 45 per cent. ( and table.)
Chemical analyses of various substances in the blood are invaluable aids in (1) the prevention of disease by alerting the patient and health care provider to potentially dangerous levels of blood constituents that could lead to more serious conditions, (2) diagnosis of pathologic conditions already present, (3) assessment of the patient's progress when a disturbance in blood chemistry exists, and (4) assessment of the patient's status by establishing baseline or “normal” levels for each individual patient.
In recent years, with the increasing attention to preventive health care and rapid progress in technology and automation, the use of a battery of screening tests performed by automated instruments has become quite common. These instruments are capable of performing simultaneously a variety of blood chemistry tests. Some of the more common screening tests performed on samples of blood include evaluation of electrolyte, albumin, and bilirubin levels, blood urea nitrogen" >blood urea nitrogen (BUN), cholesterol, total protein, and such enzymes as lactate dehydrogenase and aspartate transaminase. Other tests include electrophoresis for serum proteins, blood gas analysis, glucose tolerance tests, and measurement of iron levels.

Composition of the blood, which constitutes 8% of total body weight. From Applegate, 2000.blood bank 1. a place of storage for blood.2. an organization that collects, processes, stores, and transfuses blood. In most health agencies the blood bank is located in the pathology laboratory. It is operated by medical technologists under the direction of a pathologist.blood bank technologist a clinical laboratory scientist/medical technologist who has postgraduate education in blood banking and is certified by the Board of Registry of the American Society of Clinical Pathologists; designated as MT(ASCP)SBB. Specialists in blood bank technology perform both routine and specialized tests in blood bank immunohematology and perform transfusion services. The address of the American Association of Blood Banks is 8101 Glenbrook Road, Bethesda, MD 20814 (telephone 301-907-6582). The address of the Board of Registry of the American Society of Clinical Pathologists is P.O. Box 12270, Chicago, IL 60612. Their telephone number is 312-738-1336 and their web site is http://www.aabb.org.blood-brain barrier BBB; the barrier separating the blood from the brain parenchyma everywhere except in the hypothalamus. It is permeable to water, oxygen, carbon dioxide, and nonionic solutes, such as glucose, alcohol, and general anesthetics, and is only slightly permeable to electrolytes and other ionic substances. Some small molecules, e.g., amino acids, are taken up across the barrier by specific transport mechanisms.citrated blood blood treated with sodium citrate or citric acid to prevent its coagulation.cord blood the blood contained in the umbilical vessels at the time of delivery of the infant. It is rich in stem cells that could be used in place of bone marrow for a transplant; thus, it is sometimes collected and stored for future use.blood count determination of the number of blood cells in a given sample of blood, usually expressed as the number in a cubic millimeter; it may be either a count" >complete blood count or a count of just one of the elements such as an count" >erythrocyte count, count" >leukocyte count or a count" >platelet count. Methods include manual counts using a hemacytometer" >hemacytometer and automated counts using a flow cytometer, a Coulter counter, or other means. The blood count is useful in the diagnosis of various blood dyscrasias, infections, or other abnormal conditions and is one of the most common tests done on the blood. Called also blood cell count. (See accompanying table.)defibrinated blood whole blood from which fibrin has been separated during the clotting process.blood gas analysis laboratory studies of arterial and venous blood for the purpose of measuring oxygen and carbon dioxide levels and pressure or tension, and hydrogen ion concentration (pH). (See accompanying table.) Analyses of blood gases provide the following information:
Pa_O_₂—partial pressure (P) of oxygen (O₂) in the arterial blood (a)
Sa_O_₂—percentage of available hemoglobin that is saturated (Sa) with oxygen (O₂)
Pa_CO_₂—partial pressure (P) of carbon dioxide (CO₂) in the arterial blood (a)
pH—an expression of the extent to which the blood is alkaline or acidic
HCO₃⁻—the level of plasma bicarbonate; an indicator of the metabolic acid-base status
These parameters are important tools for assessment of a patient's acid-base balance. They reflect the ability of the lungs to exchange oxygen and carbon dioxide, the ability of the kidneys to control the retention or elimination of bicarbonate, and the effectiveness of the heart as a pump. Because the lungs and kidneys act as important regulators of the respiratory and metabolic acid-base balance, assessment of the status of a patient with any disorder of respiration and metabolism includes periodic blood gas measurements.
The partial pressure of a particular gas in a mixture of gases, as of oxygen in air, is the pressure exerted by that gas alone. It is proportional to the relative number of molecules of the gas, for example, the fraction of all the molecules in the air that are oxygen molecules. The partial pressure of a gas in a liquid is the partial pressure of a real or imaginary gas that is in equilibrium with the liquid.
Pa_O_₂ measures the oxygen content of the arterial blood, most of which is bound to hemoglobin, forming oxyhemoglobin. The Sa_O_₂ measures the oxygen in oxyhemoglobin as a percentage of the total hemoglobin oxygen-carrying capacity.
A Pa_O_₂ of 60 mm Hg represents an Sa_O_₂ of 90 per cent, which is sufficient to meet the needs of the body's cells. However, as the Pa_O_₂ falls, the Sa_O_₂ decreases rapidly. A Pa_O_₂ below 55 indicates a state of hypoxemia that requires correction. Normal Pa_O_₂ values at sea level are 80 mm Hg for elderly adults and 100 mm Hg for young adults.
However, some patients with chronic obstructive pulmonary disease can tolerate a Pa_O_₂ as low as 70 mm Hg without becoming hypoxic. In caring for patients with this condition, it is important to know that attempts to elevate the Pa_O_₂ level to the normal level can be dangerous and even fatal. It is best to establish a baseline for each individual patient before supplementary oxygen is given, and then to assess his condition and the effectiveness of his therapy according to this baseline.
The Pa_CO_₂ gives information about the cellular production of carbon dioxide through metabolic processes, and the removal of it from the body via the lungs. The normal range is 32 to 45 mm Hg. Values outside this range indicate a primary respiratory problem associated with pulmonary function, or a metabolic problem for which there is respiratory compensation.
In the newborn the normal Pa_O_₂ is 50 to 80 mm Hg. At 40 to 50 mm Hg cyanosis may become apparent. Respiratory distress in an infant who is unable to ventilate the lungs adequately will produce a drop in Pa_O_₂ level. However, there is no marked increase in Pa_CO_₂ level in some infants as in adults with respiratory distress because many infants can still eliminate carbon dioxide from the lungs even though weakness prevents inhaling an adequate oxygen supply. All infants being ventilated and receiving oxygen therapy require frequent blood gas analyses and also pH, base excess, and oxygen saturation levels to avoid oxygen toxicity and acid-base imbalance.
Blood pH gives information about the patient's metabolic state. A pH of 7.4 is considered normal; a value lower than 7.4 indicates acidemia and one higher than 7.4 alkalemia.
Because the amount of CO₂ in the blood affects its pH, abnormal Pa_CO_₂ values are interpreted in relation to the pH. If the Pa_CO_₂ value is elevated, and the pH is below normal, respiratory acidosis from either acute or chronic hyperventilation is suspected. Conversely, a Pa_CO_₂ below normal and a pH above normal indicates respiratory alkalosis. When both the Pa_CO_₂ and the pH are elevated, there is respiratory retention of CO₂ to compensate for metabolic acidosis. If both values are below normal, there is respiratory elimination of CO₂ (hyperventilation) to compensate for metabolic acidosis.
Abnormal levels of bicarbonate (HCO₃⁻) in the plasma are also interpreted in relation to the pH in the diagnosis of disturbances in the metabolic component of the acid-base balance. The normal range for HCO₃⁻ is 22 to 26 mEq per liter. Abnormally low levels of both HCO₃⁻ and pH indicate acidosis of metabolic origin. Conversely, elevations of both of these values indicate metabolic alkalosis. The kidneys maintain bicarbonate levels by filtering bicarbonate and returning it to the blood; they also produce new bicarbonate to replace that which is used in buffering. Therefore, a decreased HCO₃⁻ and an increased pH level indicate either retention of hydrogen ions by the kidneys or the elimination of HCO₃⁻ in an effort to compensate for respiratory alkalosis. Conversely, if the HCO₃⁻ level is increased and the pH is decreased, the kidneys have compensated for respiratory acidosis by retaining HCO₃⁻ or by eliminating hydrogen ions.blood gas analysis, mixed venous blood gas analysis performed on a blood sample obtained from the pulmonary artery.blood gas analysis, transcutaneous the determination of PO₂ and PCO₂ by placement of a heated electrode over the skin to get an inference of Pa_O_₂ and Pa_CO_₂.blood group the phenotype of erythrocytes defined by one or more cellular antigenic structural groupings under the control of allelic genes. In clinical practice there are four main blood groups or blood types: A, B, O, and AB (see table). In addition to this major grouping there is an Rh-hR system that is important in the prevention of erythroblastosis fetalis resulting from incompatibility of blood groups in mother and fetus.
The ABO blood group system was first introduced in 1900 by Karl Landsteiner; in 1920 group AB was discovered by van Descatello and Sturli. Identification of these four major blood groups represented a major step toward resolving the problem of blood transfusion reactions resulting from donor-recipient incompatibility. In 1938 Landsteiner and Weiner discovered another blood factor related to maternal-fetal incompatibility. The factor was named Rh because the researchers were using rhesus monkeys in their studies. Further research has uncovered additional factors in the Rh group.
Although more than 90 factors have been identified, many of these are not highly antigenic and are not, therefore, a cause for concern in the typing of blood for clinical purposes.
The term factor, in reference to blood groups, is synonymous with antigen, and the reaction occurring between incompatible blood types is an antigen-antibody reaction. In cases of incompatibility, the antigen, located on the red blood cells, is an agglutinogen and the specific antibody, located in the serum, is an agglutinin. These are so named because whenever red blood cells with a certain factor come in contact with the agglutinin specific for it, there is agglutination or clumping of the erythrocytes.
In determining blood group, a sample of blood is taken and mixed with specially prepared sera. One serum, anti-A agglutinin, causes blood of group A to agglutinate; another serum, anti-B agglutinin, causes blood of group B to agglutinate. Thus, if anti-A serum alone causes clumping, the blood is group A; if anti-B serum alone causes clumping, it is group B. If both cause clumping, the blood group is AB, and if it is not clumped by either, it is identified as group O.occult blood that present in such small amounts as to be detectable only by chemical tests or by spectroscopic or microscopic examination.peripheral blood that obtained from acral areas, or from the circulation remote from the heart; the blood in the systemic circulation.blood poisoning popular term for septicemia" >septicemia.blood pressure 1. the pressure of the blood against the walls of any blood vessel.2. the term usually refers to the pressure of the blood within the arteries, or pressure" >arterial blood pressure. This pressure is determined by several interrelated factors, including the pumping action of the heart, the resistance to the flow of blood in the arterioles, the elasticity of the walls of the main arteries, the blood volume and extracellular fluid volume, and the blood's viscosity, or thickness.
The pumping action of the heart refers to how hard the heart pumps the blood (force of heartbeat), how much blood it pumps (the cardiac output), and how efficiently it does the job. Contraction of the heart, which forces blood through the arteries, is the phase known as systole. Relaxation of the heart between contractions is called diastole.
The main arteries leading from the heart have walls with strong elastic fibers capable of expanding and absorbing the pulsations generated by the heart. At each pulsation the arteries expand and absorb the momentary increase in blood pressure. As the heart relaxes in preparation for another beat, the aortic valves close to prevent blood from flowing back to the heart chambers, and the artery walls spring back, forcing the blood through the body between contractions. In this way the arteries act as dampers on the pulsations and thus provide a steady flow of blood through the blood vessels. Because of this, there are actually two blood pressures within the blood vessels during one complete beat of the heart: a higher blood pressure during systole (the contraction phase) and a lower blood pressure during diastole (the relaxation phase). These two blood pressures are known as the systolic pressure and the diastolic pressure, respectively.
It is generally agreed that a reading of 120 mm Hg systolic and 80 mm Hg diastolic are the norms for a blood pressure reading; that is, it represents the average blood pressure obtained from a large sampling of healthy adults. In general, a blood pressure of 95 mm Hg systolic and 60 mm Hg diastolic indicates hypotension. However, a reading equal to or below this level must be interpreted in the light of each patient's “normal” reading as determined by baseline data.
On the basis of validated research on the long-term effects of an elevated blood pressure, it is generally agreed that some degree of risk for major cardiovascular disease exists when the systolic pressure is greater than or equal to 140 mm Hg, and the diastolic pressure is greater than or equal to 90 mm Hg. Life expectancy is reduced at all ages and in both males and females when the diastolic pressure is above 90 mm Hg. (See accompanying table.)Measurement of the Blood Pressure. The blood pressure is usually measured in the artery of the upper arm, with a sphygmomanometer.

Measurement of blood pressure. From Applegate, 2000. This consists of a rubber cuff and a gauge or column of mercury for measuring pressure. The rubber cuff is wrapped about the patient's arm, and then air is pumped into the cuff by means of a rubber bulb. As the pressure inside the rubber cuff increases, the flow of blood through the artery is momentarily checked.
A stethoscope is placed over the artery at the elbow and the air pressure within the cuff is slowly released. As soon as blood begins to flow through the artery again, Korotkoff sounds are heard. The first sounds heard are tapping sounds that gradually increase in intensity. The initial tapping sound that is heard for at least two consecutive beats is recorded as the systolic blood pressure.
The first phase of the sounds may be followed by a momentary disappearance of sounds that can last from 30 to 40 mm Hg as the gauge needle (or mercury column) descends. It is important that this gap" >auscultatory gap not be missed; otherwise, either an erroneously low systolic pressure or high diastolic pressure will be obtained.
During the second phase following the temporary absence of sound there are murmuring or swishing sounds. As deflation of the cuff continues, the sounds become sharper and louder. These sounds represent phase three. During phase four the sounds become muffled rather abruptly and then are followed by silence, which represents phase five.
Although there is disagreement as to which of the latter phases should represent the diastolic pressure, it is usually recommended that phase five, the point at which sounds disappear, be used as the diastolic pressure for adults, and phase four be used for children. The reason for this is that children, having a high cardiac output, often will continue to produce sounds when the gauge is at a very low reading or even at zero. In some adult patients whose arterioles have lost their elasticity, the fifth phase is also extremely low or nonexistent. In these cases, it is recommended that three readings be recorded: phase one and phases four and five. For example, the blood pressure would be written as 140/96/0. On most occasions, however, the blood pressure is written as a fraction. The systolic pressure is written as the top number, a line is drawn, and the diastolic pressure is written as the bottom number.
Errors in blood pressure measurement can result from failure of the cuff to reach and compress the artery. The cuff diameter should be 20 per cent greater than the diameter of the limb, the bladder of the cuff must be centered over the artery, and the cuff must be wrapped smoothly and snugly to ensure proper inflation. When a mercury gauge is used, the meniscus should be at eye level to avoid a false reading. Direct Measurement of Blood Pressure. Critically ill patients who require continuous monitoring of the blood pressure may have a catheter inserted into an artery and attached to a catheter-monitor-transducer system. The blood pressure is displayed on an oscilloscope at the bedside so that the patient's pressure can be determined at a glance. This intra-arterial technique of blood pressure monitoring provides accurate, objective, and continuous data on the patient's status.blood pressure, mean arterial MAP; the average pressure within an artery over a complete cycle of one heartbeat; in the brachial artery, calculated to be the diastolic pressure plus 1/3 of the difference between the systolic and diastolic pressures.blood stream bloodstream.blood urea nitrogen see urea nitrogen.blood volume 1. the total quantity of blood in the body; the volume" >plasma volume added to the volume." >red cell volume.2. a laboratory test performed to determine this. The indicators used to determine these measurements are ¹²⁵I-labeled human serum albumin for plasma volume and ⁵¹Cr-labeled erythrocytes for red cell volume. The regulation of blood volume in the circulatory system is affected by the intrinsic mechanism for fluid exchange at the capillary membranes and by hormonal influences and nervous reflexes that affect the excretion of fluids by the kidneys. A rapid decrease in the blood volume, as in hemorrhage, greatly reduces the cardiac output and creates a condition called shock or circulatory shock. Conversely, an increase in blood volume, as when there is retention of water and salt in the body because of renal failure, results in an increase in cardiac output. The eventual outcome of this situation is increased arterial blood pressure.
The blood volume in the pulmonary circulation is approximately 12 per cent of the total blood volume. Such conditions as left-sided heart failure and mitral stenosis can greatly increase the pulmonary blood volume while decreasing the systemic volume. As would be expected, right-sided heart failure has the opposite effect. The latter condition has less serious effects because the volume of the systemic circulation is about seven times that of the pulmonary circulation and it is therefore better able to accommodate a change in fluid volume. Tests. Clinical assessment of blood volume can be accomplished in a number of ways, for example, by measuring the patient's blood pressure while he is lying down, sitting, and standing. The quality and volume of peripheral pulses will give information about blood volume, as does determining the ease and speed with which a compressed vein will refill after pressure is released. Neck veins that are engorged indicate hypervolemia; the collapse of these veins indicates hypovolemia. A more accurate assessment can be done through the use of intravascular catheters such as the central venous pressure catheter, which measures pressure in the right atrium, and the swan-ganz catheter, which measures pressure on both sides of the heart.
Measurement of blood volume is accomplished by using substances that combine with red blood cells, for example, iron, chromium, and phosphate, or substances that combine with plasma proteins. In either case the measurement of the blood volume is based on the “dilution” principle. That is, the volume of any fluid compartment can be measured if a given amount of a substance is dispersed evenly in the fluid within the compartment, and then the extent of dilution of the substance is measured.
For example, a small amount of radioactive chromium (⁵¹Cr), which is widely used to determine blood volume, is mixed with a sample of blood drawn from the patient. After about 30 minutes the ⁵¹Cr will have entered the red blood cells. The sample with the tagged red blood cells is then returned by injection into the patient's bloodstream. About 10 minutes later a sample is removed from the patient's circulating blood and the radioactivity level of this sample is measured. The total blood volume is calculated according to this formula:When volume is used to arrive at the total blood volume, a dye (usually T-1824, also known as Evans blue) is injected into the circulating blood. The dye immediately combines with the blood proteins and within 10 minutes is dispersed throughout the circulatory system. A sample of blood is then drawn and the exact quantity of dye is measured. Using the information about plasma volume obtained by applying the above formula, the total blood volume can be calculated, provided the hematocrit is also known. The formula for this calculation is:whole blood that from which none of the elements has been removed, sometimes specifically that drawn from a selected donor under aseptic conditions, containing citrate ion or heparin, and used as a blood replenisher.

count

[kownt] a numerical computation or indication.Addis count the determination of the number of erythrocytes, leukocytes, epithelial cells, and casts, and the protein content in an aliquot of a 12-hour urine specimen; used in the diagnosis and management of kidney disease.blood count (blood cell count) see blood count.blood count, complete a series of tests of the peripheral blood, including the erythrocyte count, erythrocyte indices, leukocyte counts, and sometimes platelet count.blood count, differential differential leukocyte count.erythrocyte count determination of the number of erythrocytes in a unit volume of blood that has been diluted in an isotonic solution, done with an automatic counter such as a flow cytometer. Called also red blood cell or red cell count.leukocyte count determination of the number of leukocytes in a unit volume of blood, usually after the erythrocytes have been lysed and the blood has been diluted; it may be done either manually with a hemacytometer or electronically. See total leukocyte c. and differential leukocyte c. Called also white blood cell or white cell count.leukocyte count, differential a leukocyte count that calculates the percentages of different types. See also count" >total leukocyte count.leukocyte count, total a leukocyte count measuring the total number of all the types in a given volume of blood. See also differential leukocyte count.platelet count determination of the total number of platelets per cubic millimeter of blood; the direct platelet count simply counts the cells using a microscope, and the indirect platelet count determines the ratio of platelets to erythrocytes on a peripheral blood smear and computes the number of platelets from the erythrocyte count.red blood cell count (red cell count) erythrocyte count.reticulocyte count a calculation of the number of reticulocytes in 1 cu mm of peripheral blood, recorded either as an absolute number or as the percentage of the erythrocyte count. It provides a means of assessing the erythropoietic activity of the bone marrow.white blood cell count (white cell count) leukocyte count.

blood count

(blŭd kownt), Calculation of the number of red (RBC) or white (WBC) blood cells in a cubic millimeter of blood, by means of counting the cells in an accurate volume of diluted blood.

blood count

n.1. The number of red blood cells, white blood cells, and platelets in a definite volume of blood.2. The determination of such a count.3. Complete blood count.

blood count

Complete blood count, see there.

blood count

(blŭd kownt) A determination of the number of red blood cells (RBCs) or white blood cells (WBCs) in a cubic millimeter of blood; calculated by counting the cells in an accurate volume of diluted blood.

blood count

Determination of the number of red and white blood cells per millilitre of blood. The white cell count usually includes a differential count, in which the percentages of the different kinds of white cells is estimated.

blood count

(blŭd kownt) Calculation of the number of red (RBC) or white (WBC) blood cells in a cubic millimeter of blood, by means of counting the cells in an accurate volume of diluted blood.

Patient discussion about blood count

Q. what is a normal red blood cell count for breast cancer after operation A. i know that the normal count is between 4.2 to 5.9 million cells/cmm. if you have anything else- i think this question should be to the Doctor...cause even if someone here will tell you it's ok that it's a bit low- the Doctor should know that and he has your chart with all your medical information. there for i would give him a phone call to ask if it's o.k. - unless you are in the normal average i told you, then you shouldn't worry about it.

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Blood Count

Definition

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noun the number of red and white corpuscles in a blood sample

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noun the act of estimating the number of red and white corpuscles in a blood sample

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