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258 terms

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.
Neutrophilia
A significant increase in the number of neutrophilic granulocytes in the peripheral blood.
Leukocytosis
An increase in the number of leukocytes in the blood, generally caused by infection and usually transient.
Leukemia
A neoplastic, proliferative disease characterized by an overproduction of immature or mature cells of various leukocyte types in the bone marrow or peripheral blood.
Lymphoma
A solid, malignant tumor of the lymph nodes and associated tissue or bone marrow.
Infectious mononucleosis (IM)
An acute, infectious disease, commonly called mono or the kissing disease, in which there is an abnormally high number of mononuclear leukocytes in the blood. Most cases are caused by the Epstein-Barr virus. The most common serological test is the rapid slide test.
Hemolytic disease of the newborn
A neonatal disease generally caused by Rh incompatibility between mother and child, occurring when an Rh- woman carries an Rh+ fetus. Symptoms are anemia, jaundice, liver and spleen enlargement, and generalized edema. It can be controlled during pregnancy but may require intrauterine transfusion or early induced labor.
Bloodletting
The therapeutic opening of an artery or vein to withdraw blood from a particular area. Also called therapeutic phlebotomy, it is sometimes performed to treat polycythemia or congestive heart failure. One pint is collected and discarded.
Blood lavage
The removal of toxic elements from the blood by the injection of serum into the veins.
Role of the medical assistant
To help collect, process, and test urine specimens. These activities involve dealing with potentially infectious body waste, so following Universal Precautions is generally required.
Urinary system or tract
Consists of two kidneys, two ureters, a bladder, and a urethra. The kidneys remove excess water from the body and waste products from the blood in the form of urine, which then drains through the ureters into the urinary bladder. The bladder stores urine until it leaves the body through the urethra.
Nephron
The basic unit of the kidney. Each kidney contains approximately one million nephrons. Nephrons filter blood to produce urine. One of the main functions of the nephron is to remove waste material from the body. It also allows reabsorption of water and some electrolytes back into the blood.
Urinary meatus
The external opening of the urethra.
Chemical composition of urine
Approximately 95% water and 5% waste materials and other components, which include urea, ammonia, uric acid, creatinine, urobilinogen, and a few WBCs & RBCs. The presence of a few sperm cells in the urine of males is normal.
Urea
The end product of protein metabolism after ammonia is broken down by the liver.
Urochrome
The yellow pigment that gives urine its color. It is produced by the breakdown of hemoglobin.
Urination
The act of passing urine. It is also called micturition.
Urgency
An immediate need to urinate.
Urinary retention
The inability to empty the bladder.
Urinary frequency
Increased frequency can often be a symptom of a urinary tract infection, but there also may be other causes.
Incontinence
The inability to prevent release of urine. Some causes include an overfilling of the bladder and stress caused by laughing, sneezing, coughing, or lifting.
Enuresis
The involuntary discharge of urine after the age at which bladder control is normally established.
Nocturnal enuresis
Urinary incontinence during the night, also called bedwetting, which can be a symptom of a neurological disorder.
Dysuria
Painful or difficult urination, symptomatic of cystitis, infection, and many other conditions.
Polyuria
Increased output of urine.
Uropathy
Any disease or abnormal condition of any structure of the urinary tract.
Urine collection
Urine tests require between 30 and 50 mL of the specimen. When it is collected, it must be properly labeled with the patient's name, the date, and the time. Urine tests for females should be avoided during menstruation. Any medication taken by the patient must be recorded on the laboratory requisition and the patient's chart.
Home collection
Instruct patients on how to obtain the specimen. Tell them to urinate into an appropriate container, one that has a wide opening, and not to add anything else to the container. However, if you provide a container that contains preservative, caution them not to throw out the preservative. Instruct them to refrigerate the container and to keep the lid on it.
Random specimen
A single urine specimen taken at any time. A random specimen is the most common type of sample. If collection is done in a doctor's office, provide a urine specimen container, show the patient to the restroom, and ask the patient to void a few ounces of urine into the specimen container and leave it on the sink. Transport the specimen to the laboratory immediately, or refrigerate the specimen.
Clean-catch midstream specimen
A method of urine collection that may be ordered to diagnose urinary tract infections or to evaluate the effectiveness of drug therapy. The purpose of this type of collection is to obtain a urine specimen that is free from contamination. Patients completing this procedure independently need written instructions on how to make sure that the container and the urine specimen remain uncontaminated. When assisting patients, use antiseptic towelettes to clean the perineal area or the penis.
Timed specimen
Collected over a predetermined time period to obtain more specific information. Such specimens are sometimes collected 2 hours after a meal to test for diabetes. The patient should discard the first specimen and then collect all urine for the specified time, making sure that the urine does not mix with stool or toilet paper. The sample should be kept refrigerated until it is brought to the doctor's office or laboratory.
24-hour specimen
Collected to measure the amount of urine output in a 24-hour period. The urine will be tested for substances that are released sporadically into the urine.This type of collection is helpful in diagnosing renal disease, dehydration, urinary tract obstructions, and pheochromocytoma.
First-voided morning specimen
Collected after a night's sleep. It contains greater concentrations of substances that collect over time than do specimens taken during the day. A urine specimen container or clean, dry jar is used. It is best for pregnancy testing, microscopic examination, and culturing.
Catheterization
Insertion of a sterile plastic tube into the bladder, ureter, or kidney to withdraw urine. It is used to obtain a sterile urine specimen from a patient, to obtain a specimen from a patient who cannot void naturally, or to measure the amount of residual urine in the bladder after normal voiding, among other reasons. Catheterization is not routinely used because it can introduce infection.
Drainage catheter
Used to withdraw fluids.
Splinting catheter
Used after plastic repair of a ureter.
Urinalysis
The examination of urine to obtain information about body health and disease, done as part of a general physical examination or for a specific reason. The testing may be physical, chemical, or microscopic.
Physical testing of urine
Provides information about color, volume, odor, and specific gravity.
Color
Normal urine ranges from pale yellow to dark amber, depending on food and fluid intake, medications and vitamin supplements, and waste products present in the urine.
Clarity
Urine can be clear, or it can range from slightly cloudy to very cloudy. Cloudiness is also known as turbidity and sometimes indicates an abnormal condition.
Urine volume
Normal adult urine output is 600- 1800 mL per 24-hour period, with an average of 1250 mL per 24 hours.
Oliguria
Decreased output of urine, often resulting from dehydration, decreased fluid intake, shock, or renal disease.
Anuria
The complete suppression of urine formation by the kidney. It may be a result of renal or urethral obstruction or renal failure.
Urine odor
Can provide clues about the body's condition. Diseases, the presence of bacteria, and certain foods can change the odor.
Urine specific gravity
A measure of the amount or concentration of a substance dissolved in urine. It is calculated by dividing the weight of the sample by the weight of an equal amount of distilled water. The specific gravity of normal urine ranges from 1.005 to 1.030. The specific gravity of urine is lower in cases of chronic kidney disease, diabetes insipidus, overhydration, and systemic lupus.
Measuring specific gravity
Three methods are used to measure specific gravity: urinometer, refractometer, and reagent strip (dipstick).
Urinometer
A sealed glass float with a calibrated scale on the stem that measures specific gravity. At least 15 mL of urine is required.
Refractometer
An optical device that measures the refraction of light as it passes through a liquid. The degree of refraction is proportional to the amount of dissolved material in the liquid. It is faster and easier to use than the urinometer and requires only a drop of urine. It must be calibrated daily.
Reagent strips, or dipsticks
Plastic strips to which one or more pads containing chemicals are attached. The pads react to substances in the urine and change color; a chart enables you to interpret the color changes. They are available for many tests: specific gravity, pH, protein, glucose, ketones, leukocytes, erythrocytes, nitrite, bilirubin, urobilinogen, and phenylketones.
Chemical testing of urine specimens
Usually performed with reagent strips. These tests can measure liver or kidney function, metabolism of carbohydrates, acid-base balance, and urinary pH. They also show the presence of drugs or infections, ketone bodies, blood, hemoglobin, myoglobin, bilirubin, urobilinogen, glucose, protein, nitrite, phenylketones, and leukocytes.
Using reagent strips
It is important to follow the directions of the manufacturer. Keep strips in tightly closed containers in a cool, dry area, and do not remove them until immediately before testing. Never use expired strips. A dipstick may be used only once.
Urinary pH
A measure of the acidity or alkalinity (hydrogen ion concentration) of urine. The normal pH of urine is 4.5 to 8.0.
Proteinuria
The presence of protein, such as albumin, in the urine. Protein is not normally found in the urine. Its presence may signal renal disease, heart failure, hypertension, or fever, or it may be the result of heavy exercise.
Uremia
A high level of urea in the blood. Excessive amounts of urea and other nitrogenous waste products in the blood are seen in renal failure.
Uremic
Pertaining to a toxic level of urea in the blood.
Uric acid
The end product of the metabolism of purine, an important constituent of nucleic acids. A high level of uric acid in the urine may be associated with urinary calculi or gout.
Urobilinogen
A colorless compound formed in the intestines after the breakdown of bilirubin by bacteria. Some of this substance is excreted in feces, and some is reabsorbed and excreted again in bile or urine.
Urobilin
A brown pigment formed by the oxidation of urobilinogen. It is normally found in feces and in small amounts in urine.
Bilirubin
An orange-colored pigment in bile. Jaundice is a result of the accumulation in tissues of excess bilirubin in the blood.
Pyuria
The presence of pus in the urine, which may be evidence of renal disease.
Hematuria
The presence of blood in the urine, which may be a result of menstruation, urinary tract infection, or trauma or bleeding in the kidneys.
Hemoglobinuria
The presence of free hemoglobin in the urine, caused by a transfusion or drug reaction, malaria, snakebite, or severe burn.
Myoglobinuria
The presence of myoglobin in the urine, caused by injured or damaged muscle tissue.
Glycosuria
The presence of sugar (glucose) in the urine.
Nitrite
Occurs in urine when bacteria break down nitrate. It indicates a urinary tract infection.
Ketosis
An accumulation of large amounts of ketone bodies in the tissues and body fluids as a result of dehydration, starvation, uncontrolled diabetes, or taking too much aspirin. Ketones are sometimes present after general anesthesia has been administered.
Creatinine
A waste product of the metabolism of creatine. Increased quantities are found in the urine in advanced stages of renal disease.
Pregnancy test
Detects an increase in the concentration of human chorionic gonadotropin (HCG) in the plasma or urine. The presence of increased HCG can also indicate ectopic pregnancy; a hydatidiform mole of the uterus; choriocarcinoma; or cancer of the lung, breast, pancreas, stomach, or colon. The first-voided morning urine has the highest concentration of HCG.
Enzyme immunoassay (EIA) test
A more advanced type of pregnancy testing that uses either urine or serum. In this test, a sample is added through a chamber window where it migrates through the membrane and reacts with the reagents to produce a reaction. The test is easy to set up and interpret, and is designed with a control feature incorporated into the reagent pack for quality assurance of the test results.
STD testing
In response to increasing numbers of sexually transmitted diseases, the CDC recommends that all sexually active females between the ages of 15 and 25 be screened annually for chlamydia. To accomplish this, several tests called Nucleic Acid Amplification Tests (NAATs) have recently been developed. These tests use urine samples to detect the presence of chlamydia or gonorrhea.
Microscopic examination of urine
May show formed elements and also can determine the presence of cells, casts, crystals, bacteria, and other microorganisms. The first step is to use a centrifuge to obtain sediment for analysis.
Crystals
Commonly found in urine specimens. They usually do not indicate a significant disorder. They are found in large numbers in patients with renal stones.
Urinary casts
Cylinder-shaped elements that form when protein accumulates in the kidney tubules and is washed down into the urine.
Mucous threads
Found in normal urine. Increased amounts usually indicate urinary tract inflammation. They are examined under low-power magnification.
Pregnant patients
Pregnancy normally increases urinary frequency. Pregnant women are also prone to urinary tract infections. At each prenatal visit, they must have their urine checked for abnormal levels of glucose (indicative of diabetes) and abnormal levels of protein (preeclampsia or renal problems).
Elderly patients
Bladder muscles weaken with age, often leading to incomplete bladder emptying and chronic urine retention, which can cause urinary tract infections, nocturia, and incontinence.
Pediatric patients
Ask whether there are any problems with diaper rash (indicative of renal dysfunction), excessive thirst (possible diabetes), crying during urination (urinary tract infection), or bedwetting or enuresis (stress or urinary tract infections).
Diagnosing infections
There are six steps in diagnosing infections: examining the patient, obtaining one or more specimens, examining the specimen, culturing the specimen, determining the culture's antibiotic sensitivity, and treating the patient. The medical assistant should work closely with the other members of the medical team.
Throat culture
A frequently performed microbiological procedure that is often performed when the patient shows signs or symptoms of an upper respiratory, throat, or sinus infection. In most cases, a throat culture is obtained to determine whether the patient has strep throat. Left untreated, strep throat can lead to rheumatic fever. To obtain sterile specimens, such as those used for throat cultures, a sterile swab is used.
Sputum specimen
The patient should cough deeply and expectorate mucus from the lungs into a sterile container. The patient should be instructed to avoid contaminating the specimen with saliva. Follow Universal Precautions when handling sputum specimens, and wear a face shield or mask and goggles.
Wound specimens
The procedure for obtaining specimens from infected wounds is similar to that for a throat culture. Obtain representative material from a deep area and a surface area without contaminating the swab by touching areas outside the site.
Stool culture
Ordered if the physician suspects that the patient has certain diseases such as cancer or colitis or bacterial, protozoal, or parasitic infections. Patients can collect stool specimens on a clean paper plate, in a clean waxed-paper carton, or in a collection container or collection tissue. Collection containers for stool cultures do not have to be sterile.
O and P specimen
A type of stool sample examined for the presence of parasites and their ova (eggs). Both a fresh and a preserved specimen are required.
Preparing specimens for an outside laboratory
If testing is to be done by an outside laboratory, be sure to follow the collection procedures and use the collection device required by the laboratory. Maintain the samples in a state as close to their original as possible. Ensure that the container has a tight-fitting lid, and place the container in a secondary container or zipper-type plastic bag.
Transporting the specimen
Specimens can be transported to an outside laboratory during a regularly scheduled daily pickup by the laboratory, during an as-needed pickup, or through the mail.
Mailing specimens
The USPS will accept microbiological specimens with a total volume of less than 50 mL that are packaged according to strict regulations of the U.S. Public Health Service.
Direct examination
Examination of the specimen under a microscope to identify the presence of microorganisms. There are two types of procedure: preparing wet mounts and preparing potassium hydroxide (KOH) mounts.
Wet mount
A type of mount that is easy to prepare and enables quick determination of many microorganisms. It requires mixing a small amount of the specimen with a drop of normal saline (0.9% sodium chloride) on a glass slide. Then a coverslip is placed over the mixture. The physician can examine the slide directly under the microscope.
Potassium hydroxide (KOH) mount:A type of mount used for identification of a fungal infection of the skin, nails, or hair. The procedure involves the following steps
1.Suspend the specimen in a drop of 10% KOH on a glass slide.
2.Apply a coverslip.
3.Let the specimen sit for 30 minutes at room temperature.
4.Examine the slide under the microscope.
Stained specimens
Microorganisms can be seen more clearly when stained with a dye or group of dyes.
Smear
The first step in preparing a stained specimen is to prepare a smear. Apply a small amount of the specimen to a glass slide. Allow the sample to dry, then briefly heat the slide to fix the sample to the slide. Stain the smear.
Gram's stain
The stain most commonly used in examining bacteriological specimens. If the bacteria have a deep purple color, they are gram-positive. If the bacteria exhibit a pink or red color, they are gram-negative.
Acid-fast
Not readily susceptible to decolorization by acids during the staining procedure. The acid-fast nature of certain microorganisms, such as those of the genus Mycobacterium, allows microscopic examination and differentiation.
Culture media
Liquid, semisolid, and solid substances used to foster the growth of bacteria. Semisolid media are most commonly used in medical offices.
Agar
A gelatinlike substance extracted from algae that gives a semisolid culture medium its consistency.
Petri dish or plate
A covered glass or plastic dish that holds the culture medium. Handle Petri dishes only on the outside, so as to avoid contaminating them. Store them with the bottom (agar side) up.
Culturette® Collection and Transport System
A sterile, self-contained unit that holds a polyester swab and a small, thin-walled glass vial of transport medium in a plastic sleeve. It is used for obtaining and transporting specimens. (It is manufactured by Becton Dickinson Microbiology Systems.)
Selective culture media
Culture media that allow the growth of only certain kinds of bacteria. They are commonly used for specimens that normally contain bacteria, such as stools or vaginal samples.
Nonselective culture media
Media that support the growth of most organisms. For example, blood agar is a nonselective culture medium used to culture a throat swab specimen.
Special culture units
Commercially prepared units with specific purposes, such as performing rapid urine cultures or culturing vaginal specimens.
Preparing the plate
Before inoculating a culture plate, label it on the bottom (agar side) with the patient's name, doctor's name, source of the sample, date and time of inoculation, and your initials.
Bacitracin
An antibiotic used in cultures to give an early indication of the presence of group A streptococci.
Qualitative analysis
The determination of the type of pathogen by its appearance
Quantitative analysis
The determination of the number of bacteria present in a sample.
Incubation
After inoculating the plate, put it in an incubator set at 35°C to 37°C, with the bottom (agar side) up, for 24 to 48 hours.
Colony
A visible growth on a culture plate, usually resulting from a single type of bacteria.
Culture isolation
One isolated, pathogenic-appearing colony is transferred from the primary culture plate. The secondary culture plate is incubated at 37°C to allow a pure culture to grow. A pure culture contains only a single type of organism.
Sensitivity testing:Determines an organism's susceptibility to specific antibiotics in order to enable the doctor to decide which one to use to treat the infection. The test involves the following steps
1.Suspend a sample of the isolated pathogen in a small amount of liquid medium.
2.Streak the pathogen evenly on the surface of a culture plate.
3.Place small disks of filter paper containing various antimicrobial agents on top of the plate, using sterile forceps or a special dispenser.
4.Incubate the plate at 37°C for 1 day.
Quality control
All staining reagents should be checked frequently for effectiveness. All slides must be checked. All devices with temperature controls should be checked every day. All reagents and media must be used before the expiration date and evaluated for sterility.
Clinical Laboratory Improvement Amendments of 1988 (CLIA '88)
A law enacted by Congress placing all laboratory facilities involved with human health and disease under federal regulations administered by the Health Care Financing Administration (HCFA) and the CDC. As a result, laboratories must meet complex standards, and medical assistants may perform only certain types of tests.