CH 24 Laboratory Procedures

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Medical assistant's role

Depending on the laws of the state in which you live, you may collect and process blood specimens, conduct blood tests, and complete necessary paperwork.

Hematology

The study of blood and blood-forming tissues.

Functions of blood

To distribute oxygen, nutrients, and hormones to body cells; to eliminate waste products from body cells; to attack infecting organisms or pathogens; to maintain the body's acid-base balance; and to regulate body temperature.

Hematopoiesis

The normal formation and development of blood cells in the bone marrow.

Whole blood

Consists of plasma and the formed elements. In adults, total blood volume normally makes up 7% to 8% of body weight, or 70 mL/kg of body weight in men and about 65 mL/kg in women. Blood is pumped through the body at a speed of about 30 cm per second, with complete circulation in 20 seconds.

Plasma

The liquid in which the other components of blood are suspended. Plasma accounts for 55% of the body's total blood volume. Water makes up about 90% of plasma. About 9% is protein and 1% is other substances, including carbohydrates, fats, gases, mineral salts, protective substances, and waste products. Free of its formed elements and particles, plasma is a clear, yellow fluid. When a tube of blood is centrifuged, the plasma rises to the top.

Formed elements, or blood cells

Red cells (erythrocytes), white cells (leukocytes), and platelets (thrombocytes). Blood cells constitute about 45% of the body's total volume of blood. An older term for a formed element is blood corpuscle.

Blood gas

Dissolved gas in the liquid part of the blood. Blood gases include oxygen, carbon dioxide, and nitrogen.

Bone marrow

Found in the cavities of all bones. It may be present in two forms: red and yellow. Yellow marrow is inactive and is composed mostly of fat tissue. Red marrow is active in the production of most types of blood cells. By age 18, red marrow is found only in the vertebrae, ribs, sternum, skull bones, and pelvis.

Erythrocyte

Also known as a red blood cell (RBC). A mature RBC is made up of lipids and proteins to which hemoglobin molecules are attached. RBCs play a vital role in internal respiration, the exchange of gases between blood and body cells. They are disk shaped and have concave sides.

Erythropoiesis

The process of erythrocyte production. This process develops in the embryonic yolk sac, liver, and spleen. It is ultimately located in the red bone marrow during late fetal development, childhood, and adult life.

Erythropoietin

A glycoprotein hormone, produced primarily by the kidneys and also secreted by the liver, that stimulates erythropoiesis. It can cross the placental barrier.

Reticulocyte

The last stage of the immature erythrocyte. This cell has a nucleus and is found both in the bone marrow and, often, in peripheral blood.

Transferrin

A specific transport protein in the blood. It binds iron and transports it back to the bone marrow for hemoglobin synthesis.

Hemoglobin

The iron-containing pigment of RBCs that carries oxygen from the lungs to the tissues.

Hemagglutination

The coagulation of erythrocytes.

Hemagglutinin

A type of antibody that agglutinates erythrocytes.

Rouleaux formation

A configuration of RBCs having the appearance of stacked coins.

Leukocyte

Also known as a white blood cell (WBC). Through phagocytosis, it protects the body against infection. Leukocytes are divided into two groups: granular and nongranular.

Granular leukocytes

Basophils, eosinophils, and neutrophils.

Basophils

Produce histamine, which plays a major role in allergic reactions.

Eosinophils

Capture invading bacteria and antigen-antibody complexes through phagocytosis.

Neutrophils

Attack invaders (specifically target bacteria) and release pyrogens, which cause fever.

Nongranular leukocytes

Lymphocytes and monocytes.

Lymphocytes

The smallest leukocytes, which contain the largest nuclei. They include B cells and T cells. B lymphocytes produce antibodies to combat specific pathogens. T lymphocytes regulate the immune response.

Monocytes

Large leukocytes in the bloodstream with oval or horseshoe-shaped nuclei. Their major functions are phagocytosis and synthesis of various biological compounds, including transferrin, complement, interferon, and certain growth factors.

Macrophages

Monocytes that mature outside the circulatory system, distributed in tissues throughout the body. They have a variety of names (often depending on their location in the body), such as histiocytes, Kupffer cells, osteoclasts, and microglial cells.

Phagocytes

Cells that have the capacity for phagocytosis. Macrophages, as well as most of the leukocytes, are phagocytes. Large phagocytes can destroy worn-out RBCs or bacteria. They are found in the spleen, thymus, and lymphoid tissues.

Phagocytosis

The process by which cells engulf and ingest microorganisms.

Platelets

Metabolically active anuclear cell fragments produced in the bone marrow that assist in blood coagulation and clotting. They are also called thrombocytes. Normally, between 130,000 and 400,000 platelets are found in 1 cubic milliliter of blood.

Megakaryocytes

Precursors of platelets. They are the largest cells found in the bone marrow, and they have a nucleus with many lobes. They are normally not present in circulating blood.

Serology

The study of blood serum based on antigen-antibody reactions in vitro.

Serum

The liquid portion of blood that remains after the clotting proteins and cells have been removed. It differs from plasma in that it does not contain fibrinogen, a protein involved in clotting.

Antigen

A substance on cells whose presence in the body stimulates the body's immune response. Antigens produced by the body itself are autoantigens; antigens on other cells are foreign antigens.

Antibody

A protein produced in response to a specific antigen. It defends the body against infection.

Agglutination

An antigen-antibody reaction in which a solid antigen clumps together with a soluble antibody.

Agglutinin

An antibody that interacts with antigens, resulting in agglutination.

Agglutinogen

Any antigenic substance that causes agglutination.

Opsonization

A process by which antibodies or complements render bacteria more susceptible to phagocytosis by leukocytes. It is also called opsonification.

Immunology

The study of the reaction of immune system tissues to antigenic stimulation.

Immune

Protected by antibodies against infective or allergic disease.

Immune response

A defense function of the body that produces antibodies to destroy invading antigens and cancer cells.

Antiserum

A serum of animal or human origin that contains antibodies against a specific disease. It is also called immune serum. Antiserums (or antisera) do not provoke the production of antibodies. There are two types: antitoxin and antimicrobial.

Complement

Protein molecules that are chief humoral mediators of antigen-antibody reactions in the immune system. Complement proteins stimulate phagocytosis and inflammation.

Classification of immunoglobulin

In response to specific antigens, immunoglobulins are formed in the bone marrow, the spleen, and all lymphoid tissue of the body except the thymus. All antibodies are immunoglobulins.

Collecting blood

The two common ways to collect blood are phlebotomy and capillary puncture. Some, but not all, states permit medical assistants to obtain blood samples. You should know the appropriate laws of your state.

Phlebotomy

The insertion of a needle or IV catheter into a vein to draw blood. It is also called venipuncture or venesection. Phlebotomy is the most common method of collecting blood for hematological testing. The most common site for venipuncture is the median cubital vein. The cephalic vein of the forearm, the basilic vein of the forearm, and the veins in the back of the hand are also sometimes used.

Capillary puncture

A superficial puncture of the skin with a sharp point that releases a smaller amount of blood than venipuncture. It is also called a finger stick. Capillary puncture in adults and children is usually performed on the great (middle) finger or the ring finger. Try to use the patient's nondominant hand, and do not reuse a previous puncture site. Capillary puncture in infants is usually performed on one of the outer edges of the underside of the heel. The rear curve of the heel should never be punctured.

Needlestick Safety and Prevention Act

In response to the Needlestick Safety and Prevention Act, which was signed into law in November 2000, OSHA revised the Blood-Borne Pathogens Standard.

Documentation

Maintain the quality control log, reagent control log, equipment maintenance log, reference laboratory log, and daily workload log, as applicable.

Quality control log

Shows the completion of every quality control check conducted on a piece of equipment. The testing equipment must be calibrated regularly in accordance with manufacturer's guidelines. Calibration routines are performed on a set of standards, the values of which are already known.

Control sample

A specimen with a known value that is used every time a patient sample is processed. Using a control sample serves as a check on the accuracy of the test.

Reagent

A chemical or chemically treated substance that reacts in specific ways when exposed under specific conditions.

Reagent control log

Shows the quality testing performed on every batch or lot of reagent products. Control samples or standards are run every time you open a new supply of testing products, such as staining materials, culture media, and reagents.

Equipment maintenance record

Documents any maintenance done on laboratory equipment.

Reference laboratory log

Lists specimens sent to another laboratory for testing.

Daily workload log

Shows all procedures completed during the workday.

Laboratory requisition form

As a medical assistant, it is your responsibility to ensure that the laboratory requisition form is properly completed. Missing information can lead to improper testing or lost results. The completed form should be included with the specimen collected or sent with the patient to the laboratory. Be sure to include the following information on all requisitions:
• Patient's full name, sex, date of birth, and address
• Patient's insurance information
• Physician's name, address, and phone number
• Source of the specimen
• Date and time of the specimen collection
• Test(s) requested
• Preliminary diagnosis
• Any current treatment that might affect the results

Patient record

Record test results in the patient's record, and properly identify any unusual findings. Remember that only a physician is qualified to interpret test results, so these results should not be communicated to the patient until the physician has had an opportunity to review the information.

Equipment needed

Typically includes a needle, syringe, tube, or lancet to draw blood; alcohol and cotton balls or alcohol wipes; sterile gauze; adhesive bandages; and a tourniquet.

Venipuncture collection needle

Specially designed needle used with an evacuated tube blood collection system ranging from 19 to 23 gauge and 1″ to 1½″ in length.

Blood lancet

A small, sterile, disposable instrument used for skin or capillary puncture.

Automatic puncturing device

A spring-loaded mechanism equipped with a disposable lancet for capillary puncture.

Micropipette

A calibrated glass tube for measuring small, precise volumes of fluids used in capillary puncture.

Unopette®

A disposable micropipette blood-diluting system used to perform manual blood counts. (It is manufactured by Becton Dickinson Vacutainer® Systems.)

Reagent strip

Used with freshly collected blood droplets in capillary puncture. It is also referred to as a dipstick. Blood is dropped or smeared on the strip. Some of the blood tests performed in this way are those for determining blood glucose levels, sickle cell anemia, infectious mononucleosis, and rheumatoid arthritis.

Smear slide

A prepared microscope slide to which freshly collected blood is applied.

Butterfly needle set

A device used to collect blood samples from individuals with small or fragile veins. It consists of a needle with plastic wings, flexible tubing, an adapter, and a collection device. A butterfly system generally uses a smaller needle (23-25 gauges) than other venipuncture techniques do. Once inserted, the needle is held in place by holding the wing of the needle while the collection device is manipulated.

Engineered safety devices

In response to the Needlestick Safety and Prevention Act, a number of engineered safety devices have been developed. These devices are intended to reduce the possibility of needlestick injuries.

Evacuation tube

The most common evacuation system is the Vacutainer® system (manufactured by Becton Dickinson Vacutainer® Systems). It uses a special needle, a needle holder/adapter, and collection tubes that have been sealed to maintain a slight vacuum. Some tubes are prepared with additives needed to process the blood sample for testing, such as anticoagulants. The tube stoppers are color-coded according to the type of additive used.

Collection tubes

No matter which method is used to collect blood, the samples must immediately be mixed with the appropriate additives in the correct collection tubes before they are transported to the laboratory for testing. Each laboratory may choose which tubes to use for a particular test.

Anticoagulants

Substances that prevent blood clotting. Three anticoagulants commonly used in the hematology laboratory are heparin, sodium citrate, and ethylenediaminetetraacetic acid (EDTA).

Heparin

A substance produced naturally by basophils and mast cells. Heparin acts in the body as an antithrombin factor to prevent intravascular clotting. As an additive in blood collection, heparin is used in electrolyte studies and tests for arterial blood gasses. Heparin also is used as an anticoagulant in the prevention and treatment of thrombosis and embolism.

Sodium citrate

A white granular powder, used as an anticoagulant in transfusions and coagulation studies.

EDTA

Used as an anticoagulant additive in hematology studies. It also is used to treat exposure to toxic chemicals; it chemically "grasps" toxic substances, thereby making them nonactive. Excessive EDTA produces a shrinkage of the erythrocytes.

Antiseptic

A substance that inhibits the growth and reproduction of microorganisms. Some examples of antiseptics are 70% isopropyl alcohol, povidone-iodine (Betadine®), and benzalkonium chloride (Zephiran®).

Betadine®

An antiseptic recommended for use in arterial blood gas studies and blood culture draws.

Zephiran®

A trade name for benzalkonium chloride, used in blood collection to detect alcohol levels.

Labeling containers

After blood is drawn, all tubes, slides, and other containers should be labeled with the patient's name, the date and time of collection, the initials of the person who collected the specimen, and any other required information, such as the patient's identification code.

Tube size

Tubes range in size from 15 mL down. Most tubes used for adults range from 3 to 10 mL, and those for children range from 2 to 4 mL. Microcapillary collection tubes hold less than 1 mL.

Order of draw tubes

The National Committee for Clinical Laboratory Standards publishes the recommended order of draw as follow: yellow, light blue, red, red/black (tiger stripes), green, lavender, and gray.

Tourniquet

A device used to control hemorrhage or to distend veins for the withdrawal of blood. A tourniquet increases resistance in the venous blood flow. It should not remain on the patient's arm longer than 1 minute. Tourniquets are available in many materials. They are placed on the upper arm of the patient, 3 to 4 inches above the elbow.

Gloves

Made from a variety of materials, such as vinyl, latex, and nitrile. Latex gloves are the most commonly used, but some individuals are highly allergic to latex. Nitrile gloves are more tear-resistant and feel more comfortable on the hand.

Needle disposal

Needles must be properly disposed of in appropriate biohazard containers. They should not be laid down or placed on any surface and should not be recapped.

Assembling equipment and supplies

After reviewing the test order, make sure that you have the appropriate equipment to collect the required samples.

Preparing patients

After greeting the patient, ask for the patient's full name to verify that the patient is the one listed on the order. Confirm that the patient has followed any pretest restrictions, such as fasting before the appointment.

Universal Precautions

It is important to follow Universal Precautions during all phlebotomy procedures. Before collecting blood, make sure to wash your hands and put on examination gloves. When you have finished drawing blood, properly dispose of used supplies and disposable instruments, disinfect the area, remove the gloves, and wash your hands.

Chain of custody

A means of ensuring that a specimen obtained from a patient is correctly identified, is under the uninterrupted control of authorized personnel, and has not been altered or replaced. It is established for blood samples drawn for drug and alcohol analysis as well as for specimens taken in cases of medicolegal importance such as rape.

Handling an exposure incident

Following Universal Precautions should reduce your risk of exposure, but accidents sometimes still happen. If you suffer a needle stick or other injury that results in exposure to blood or blood products from another person, report the incident to the appropriate staff members immediately. Wash the injured area carefully, and apply a sterile bandage. Record the time, date, and nature of the incident and the names of the people involved.

Syncope

Fainting, usually caused by pain, fright, and the sight of blood. Syncope lasts only 1 to 2 minutes. If fainting occurs, the procedure must be terminated immediately. The patient should be placed lying down, with legs elevated. The event should be completely documented on the laboratory log. Assistance should be called for, and the patient should never be left alone.

Failure to obtain blood

There are several factors that may make blood collection impossible. It is important to remain calm and to determine the cause of the problem. If you cannot collect a good sample on the second try, do not make a third attempt. Ask for assistance.

Scarred and sclerosed veins

Do not draw blood from injured or diseased areas.

Hematoma

A pooling of blood just under the skin. It is caused by blood leaking into the tissues. When it happens, pressure should be applied to the area for 3 minutes, and then ice should be applied.

Hemorrhage

Excessive bleeding.

Petechiae

Tiny red spots appearing on the skin as a result of small hemorrhages within the dermal layer. They may be a complication of keeping a tourniquet in place for longer than 2 minutes.

Hematological tests

May be performed on venous or capillary whole blood specimens. These tests include blood cell count, morphological studies, coagulation tests, and the erythrocyte sedimentation rate test.

Erythrocyte sedimentation rate (ESR, or sed rate) test

Measures the rate at which RBCs settle out in a tube of unclotted blood, expressed in millimeters per hour. The test determines the degree of inflammation in the body. There are several testing systems available, and it is important to adhere to the manufacturer's instructions in using each test. Results are sensitive to temperature and freshness of the samples, precise position of the sample tube, and vibrations. The normal rate at which RBCs fall is 1 mm every five minutes.

Bleeding time test

Gives information about the integrity of the patient's platelet function. A prolonged bleeding time indicates such conditions as low platelet count and dysfunction of the platelets. Aspirin impairs the platelets' ability to form aggregates. Antihistamines also interfere with bleeding time.

Blood smears

Used to obtain a differential cell count and to reveal abnormal RBC morphology for anemia. To prepare a blood smear slide, apply a drop of blood to the slide, ¼ inch from the frosted end, and use a spreader slide at a 30- to 35-degree angle to spread the blood droplet.

Stains

Used to selectively color microscopic objects and tissues for study.

Morphological studies

Used in the examination of a blood smear for the purpose of recording the appearance and shape of cells, with special note made of abnormal cell size, shape, or content and abnormal organization of cells.

Coagulation tests

Used to identify bleeding problems, generally scheduled before surgery or to monitor therapeutic drug levels.

Hemoglobin (Hgb or Hb) tests

Used to measure the concentration of hemoglobin in the blood. Hb testing can be performed on either venous or capillary whole blood specimens. Among the types of hemoglobin are hemoglobin A, hemoglobin F, and hemoglobin S. Hemoglobin level is high at birth but declines during childhood. It then increases at different ages.

Hemoglobin A

Normal adult hemoglobin.

Hemoglobin F (HbF)

Fetal hemoglobin, the normal hemoglobin of the fetus and the predominant hemoglobin variety in the fetus and neonate. Most HbF is replaced by hemoglobin A in the first days after birth.

Hemoglobin S

Sickle-shaped hemoglobin, found in sickle cell anemia and also in sickle cell trait. It is found exclusively in persons of African descent. About 8% of African Americans in the United States are affected.

Blood count

The complete blood count (CBC) is the most common laboratory procedure ordered on blood. It includes the red blood count (RBC), white blood count (WBC), differential WBC, and platelet count, as well as a hematocrit determination and a hemoglobin determination.

Hematocrit (Hct)

The relative volume of RBCs in a blood sample after the sample has been spun in a centrifuge (packed cell volume), expressed as a percentage. The erythrocytes collect at the bottom of the tube. Above the packed erythrocytes is a layer of leukocytes and thrombocytes. This layer is called the buffy coat. Above the buffy coat is the plasma, which is free of cell elements.

Serological tests

Used to detect the presence of specific substances in blood serum (e.g., disease antibodies, drugs, hormones, and vitamins) and to determine blood types.

Amylase test

Amylase is an enzyme of the exocrine pancreas. Its function is to break down starches into dextrin and maltose during the digestive processes. Blood serum is tested for increased amylase levels, which may occur in patients with a perforated ulcer, salivary gland disease, obstruction of the pancreas duct, or cancer of the pancreas. Decreased amylase levels are seen in patients with extensive destruction of the pancreas and hepatic insufficiency.

Western blot

Confirms the presence of HIV.

ABO blood group test

Determines blood groups and type.

Rh blood groups

Blood that has the Rh (or D) antigen on the surface of its RBCs is Rh positive (Rh+), and blood that does not have the antigen is Rh negative (Rh−). If an individual with Rh− blood receives a transfusion of Rh+ blood, anti-Rh agglutinin forms, and subsequent transfusions may result in serious reactions.

Crossmatching

A test to establish blood compatibility before transfusion that simulates the transfusion in a test tube by mixing donor cells with recipient serum or plasma. A compatible crossmatch is one in which no reaction occurs between cells and serum at room and body temperature.

Universal donor blood

Uncrossmatched blood, which may be requested from a blood bank by a physician in emergency situations. This uncrossmatched blood is usually group O, Rh- with packed RBCs.

Clinical chemistry

The use of computerized instruments to perform one or more tests on a single blood sample. Tests are conducted for such substances as alcohol, potassium, sodium, cholesterol, lead, phenobarbital, and cocaine.

Glucose testing

Can be performed on whole blood, plasma, or serum, but plasma and serum free of hemolysis are preferred. Glucose concentration is stable for up to 8 hours at room temperature and up to 72 hours under refrigeration. Blood should be centrifuged and separated from the clot and cells as soon as possible or within 30 minutes, unless a specific additive (such as fluoride) is used. If the blood must be stored for several hours, fluoride-oxalate is the anticoagulant mixture of choice.

Glucose tolerance test

Performed by giving a certain amount of glucose to a patient, then drawing blood samples at specified intervals and measuring the blood glucose level in each sample. Patients with diabetes may have normal fasting blood glucose levels, but they may be unable to produce a sufficient amount of insulin when needed to metabolize normal loads of carbohydrates. In these cases, blood glucose levels rise to abnormally high levels and remain high for a long period of time.

Hemoglobin A1c (HgBA1c)

A test used to monitor the health of patients with diabetes. The HgBA1c test is a useful tool for monitoring the overall stability of the patient's blood glucose. When blood glucose levels are elevated, the glucose molecules bind with hemoglobin to form HgBA1c. Once HgBA1c is formed, it remains for the life of the RBC (90 to 120 days). The test may be sent to an outside reference laboratory, and some physicians' offices have the equipment necessary to perform this test in the office laboratory.

Arterial blood gas

Oxygen and carbon dioxide in arterial blood are measured by various methods to assess the adequacy of ventilation and oxygenation and the acid-base balance. Oxygen saturation of hemoglobin is normally 95% or higher.

Arterial pH

The hydrogen ion concentration of arterial blood. The normal range is 7.35 to 7.45.

Neonatal blood collection

Neonatal screening tests are commonly conducted to detect increased bilirubin, phenylketonuria (PKU), and hypothyroidism. PKU and thyroid tests are required by law in the United States. The common site for collection of blood is the infant's foot. Care must be taken not to damage the heel bone, which could cause osteomyelitis in the newborn.

PKU screening

Tests the infant's ability to metabolize phenylalanine. Increased phenylalanine in the blood can result in brain damage and mental retardation.

Microscope

The instrument most often used in the physician's office laboratory (POL). Microscopes are used to examine blood smears, perform blood cell counts, and identify body fluid samples.

Oil-immersion objective

The objectives of a microscope contain magnifying lenses that increase the magnification of the oculars by another 10 × to 40 × . The oil immersion objective is designed to be lowered into a drop of immersion oil placed directly over the prepared specimen under examination. This design eliminates the air space between the microscope slide and the objective, thereby reducing the loss of light and creating images that are sharper and brighter.

Centrifuge

A laboratory machine used to separate particles of different densities within a liquid by spinning them at very high speeds.

Hemocytometer

A special microscope slide used primarily for counting blood cells that can also be used for counting platelets, sperm, and other cells. The most commonly used hemocytometer is the Neubauer type.

Hyperglycemia

A higher-than-normal blood glucose level. The most common cause of hyperglycemia is diabetes mellitus. Other conditions that can cause hyperglycemia are hyperthyroidism, Cushing's syndrome, acromegaly, obesity, severe liver or kidney damage, alcoholism, and elevated levels of the hormones estrogen, epinephrine, or norepinephrine.

Hypoglycemia

Abnormally low levels of glucose in the blood, below 50 mg/dL. The most common cause of hypoglycemia is insulin overdose in patients with unstable insulin-dependent diabetes mellitus.

Hemophilia

A hereditary disorder of clotting factors, in which blood fails to coagulate at a wound site.

Hyperlipidemia

A higher-than-normal level of lipids, especially cholesterol, in the blood.

Visual indications

Hyperlipidemia gives plasma or serum a milky, or turbid, appearance. Sometimes the plasma or serum will have a pale, watery appearance as a result of protein disorders or kidney disease. In certain types of cancers, the color of the serum may be green, attributable to heme (part of hemoglobin).

Extramedullary hematopoiesis

In abnormal circumstances, the spleen, liver, and lymph nodes revert back to producing immature blood cells. This reversion can be the result of aplastic anemia, infiltration by malignant cells, leukemia, or hemolytic anemias.

Anemia

A reduction in the number of circulating RBCs per cubic millimeter. Hemoglobin content is less than that required to provide the oxygen needed by the body.

Abnormal erythrocytes

Vary from the norm in terms of size, shape, and color. Normal mature erythrocytes are biconcave and disc-shaped and lack a nucleus.

Anisocytosis

An abnormal condition characterized by excessive inequality in the size of erythrocytes.

Macrocyte

An abnormally large erythrocyte.

Megalocyte

An erythrocyte that is larger than average.

Microcyte

An abnormally small erythrocyte.

Poikilocytosis

Variation in the shapes of erythrocytes.

Schistocyte or schizocyte

An erythrocyte that has been fragmented during circulation.

Ovalocyte

An erythrocyte that is oval in shape. It is also called an elliptocyte.

Spherocyte

An erythrocyte that is spheroid in shape, having a decreased ratio of surface area to volume.

Target cell

An abnormally thin RBC with a dark center and a surrounding ring of hemoglobin. Also called leptocytes, target cells occur in anemia and jaundice.

Sickle cell

An erythrocyte that is sickle- or crescent-shaped. Such cells are produced by the polymerization of hemoglobin and occur in hereditary anemias.

Hypochromia

A condition in which cells have decreased hemoglobin.

Polycythemia

An above-normal concentration of erythrocytes in the circulating blood. It is also called erythrocytosis.

Polycythemia vera

A blood dyscrasia (disease) characterized by abnormally increased levels of erythrocytes, leukocytes, and thrombocytes. It is also called erythremia.

Neutropenia

A severe decrease in the number of neutrophilic granulocytes in the peripheral blood.

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