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Slide 1 Under the Microscope 101 An Introduction to Pathology and Laboratory Medicine Slide 2 Careers in Pathology and Laboratory Medicine A highly skilled team of pathologists and medical laboratory scientists, technicians and specialists play a critical role in evaluating information needed to give the best care to an ill or injured patient. In fact, more than 70 percent of medical decisions made by physicians are based on laboratory findings. Some of the professionals who work in medical laboratories include the: Pathologist A pathologist is a medical doctor who examines tissues and is responsible for the accuracy of laboratory tests. The pathologist and the patient’s doctor consult on which tests to order, interpretation of test results, and appropriate therapy. Medical Laboratory Scientist and Medical Laboratory Technician Medical laboratory scientists and Medical laboratory technicians perform tests in all areas of the medical laboratory. They are also responsible for confirming the accuracy of test results and operating complex electronic equipment. Cytotechnologist Cytotechnologists examine human cell samples under the microscope for early signs of cancer and other diseases. The cytotechnologist analyzes subtle cell changes and compares these changes to normal cell findings for that body site. Histotechnologist and Histotechnician The Histotechnologist and Histotechnician prepare small sections of body tissues for microscopic examination by a pathologist. The laboratory professionals work closely with the pathologist to process tissue biopsies removed during surgery. 1 Phlebotomy Technician The Phlebotomy Technician collects blood samples from patients for analysis in the laboratory. The laboratory depends on the phlebotomy technician to collect specimens properly from the patient to produce high quality, accurate laboratory test results. Slide 3 Departments in the Medical Laboratory Most medical laboratories are divided into distinct departments that separate the types of tests performed based on sample type and intended result. The major areas and their functions are: Clinical Chemistry The clinical chemistry department performs hundreds of quantitative analyses on a variety of body fluids. Common chemistry procedures include testing for glucose, cholesterol, hormones, and electrolytes. Blood Bank (Immunohematology) The blood bank provides blood typing and compatibility testing for both donors and recipients and ensures the safety of the blood supply. Immunology/Serology Immunologic/serologic testing evaluates antibodies and/or antigens that may be indicative of many types of infectious disease. This is important in not only confirming a diagnosis, but also in treating and managing various conditions. Microbiology The microbiology section identifies microorganisms that may be causing disease (pathogens). The microbiology department also provides information regarding appropriate antibiotics to use as treatment for various pathogens. Urinalysis The urinalysis department screens urine samples for evidence of kidney disease or bladder infections. Coagulation Coagulation procedures are performed to identify possible bleeding or clotting disorders. Coagulation testing is also used to monitor anticoagulant therapy. 2 Hematology They hematology department performs tests that are important in diagnosing many disorders such as anemia and leukemia. Slide 4 Complete Blood Count One of the most useful and commonly ordered hematology tests is the complete blood count (CBC). The CBC includes the number of white blood cells (WBC), red blood cells (RBC), and platelets as well as the measurement of hemoglobin and hematocrit. These measurements are performed using sophisticated instruments. The CBC also includes the percentage differential count of the white blood cells. The differential is performed on a carefully prepared and stained blood smear using either venous blood or blood from a fingerstick. A drop of blood is put on a glass microscope slide and spread out using another slide. The smear is allowed to dry and then stained using a special hematological stain which allows the various components of the blood to stain differently from each other. The staining may be done by hand but is more commonly done in an automated staining instrument. The most common type of stain in use today is Wright’s stain. The stained smear is then evaluated by the medical laboratory scientist or medical laboratory technician using the microscope. Slide 5 Blood Cells The following discussion and images describe and illustrate some of the types of cells normally seen on a differential blood smear. I. Leukocytes: white blood cells A. Granulocytes: destroy bacteria and other bloodstream invaders. There are three subtypes of granulocytes. They were named for the dye color they take up when stained with Wright’s stain. 3 Slide 6 1. Segmented neutrophils are the oldest cells in the granulocytic series and are the most common leukocyte seen in the blood of a normal adult. They are characterized by 2 to 5 connected lobes in the nucleus, and stain dark with thick strands of chromatin. The cytoplasm is pink with fine pinkish-tan granules. 2. Eosinophils have granules that take up the red dye eosin. They are characterized by large red to reddish-orange granules which are uniform in size and shape. 3. Basophils have granules that take up the blue (basic) dye. They are characterized by blue-black granules that vary in size and number and usually obscure the nucleus. Slide 7 B. Lymphocytes have a very dark nucleus, a clumped nuclear chromatin pattern, and very little cytoplasm (dark blue). They are usually slightly larger than a mature red blood cell. There are several classes and functions of lymphocytes -- the primary functions being production of antibodies and developing cellular immunity. Lymphocyte subclasses are not distinguishable on the differential smear. Slide 8 C. Monocytes are the largest of the normal white blood cells. They are characterized by an irregular, folded, or horseshoe shaped nucleus, with lighter (lavender) staining chromatin. The cytoplasm is sometimes foamy, and it may contain holes known as vacuoles. Monocytes, like granulocytes, are involved in destruction of bloodstream invaders. This type of WBC is increased when bacterial infections or monocytic leukemia are present. In addition, monocytes are found in tissue where they are known as macrophages. 4 Slide 9 II. Erythrocytes are commonly known as red blood cells. They appear as biconcave discs. They contain hemoglobin and function to carry oxygen to tissues. Slide 10 III. Thrombocytes are commonly known as platelets. They are small cells (even smaller than red blood cells) with bits of blue or purple cytoplasm and no nuclear structure. The primary function of platelets is in blood clotting processes. Slide 11 Abnormal Blood Cells Abnormal differential blood smears may indicate a variety of disease states. Slide 12 Infection: Mononucleosis The differential blood smear may demonstrate the presence of a bacterial or viral infection. This image shows a reactive lymphocyte as it might appear in infectious mononucleosis. The lymphocyte shows a characteristic cytoplasm with a dark blue border. Slide 13 Sickle Cell Anemia Sickle cell anemia is characterized by abnormally shaped, "sickled" red blood cells. It is a genetic disorder, primarily found in the African-American population. An individual who inherits a sickle cell gene from both parents (homozygous) will have the severe anemic disease. If the gene is inherited from only one parent (heterozygous), the individual has the sickle cell trait, but not the anemic state. 5 Slide 14 Leukemia Leukemias are characterized by increased proliferation of white blood cells. A variety of leukemias are classified on the basis of the cell type affected. This image illustrates chronic granulocytic (myelogeneous) leukemia. It affects the granulocytes, increasing the younger cells in the granulocytic series. Very young cells, which are normally only seen in the bone marrow, may be seen in the peripheral blood smear. Slide 15 Identifying Microorganisms Laboratory professionals also work closely with doctors, nurses, and other members of the health care team to diagnose and manage diseases that are caused by microorganisms - bacteria, viruses, parasites, and fungi. In the microbiology laboratory, they analyze and identify these microorganisms and report the results to the physician for use in treating the patient. In many cases, the doctor must rely on the medical laboratory scientist's identification of the microorganism to select the best treatment. Slide 16 Bacteria The appearance of the microorganism on an agar plate or in the liquid media gives the medical laboratory scientist preliminary clues to the identity of the microorganism. After observing the bacterial colonies in the agar plate, the next step in the identification is to look at the microorganism through the microscope. The microorganisms are placed on a glass slide and stained with a special stain called a Gram stain. In a Gram stain, the bacteria will appear gram-positive (purple staining) or gram-negative (pink staining) depending on the structure of the cell wall. The Gram staining reaction plus the shape of the individual microorganisms are important first steps in identification. The two most common shapes are cocci and bacilli. Cocci are round-shaped cells and bacilli are bacteria with short, rectangular shapes. 6 Slides 17 and 18 Bacteria, continued Notice that both gram-positive cocci (Slide 17) and gram-negative bacilli (Slide 18) are much smaller than blood cells. Once the pathogenic bacteria are isolated and identified, the medical laboratory scientist will test the bacteria to determine which antibiotics will be effective for treating the infection. Antibiotics work against bacteria by causing irreversible damage to their cell walls or by preventing their multiplication. These drugs work together with the body's natural disease-fighting forces to eliminate the pathogens. Since bacteria are living microorganisms, they can develop resistance to antibiotics; therefore, each bacterium is tested for susceptibility to a variety of antibiotics. Slide 19 Viruses Viruses cannot be grown on regular plate media because they can only reproduce in living cells. This group of microorganisms is grown in living tissue cultures. The cells are inoculated with the patient's specimen, such as blood or urine, and are then incubated. The cells are kept moist and given nutrients by adding liquid growth media. Slide 20 Fungi The oval cells in this slide are not bacteria. They are a form of fungi called yeast which reproduce by budding. Usually humans are not bothered by yeast because yeast is part of our body's normal flora. However, when the body's immune system is not working properly, or if antibiotics are used for a long time, yeast may multiply and cause an infection. Yeast can cause diaper rash in infants and an oral condition called thrush in AIDS patients. 7 Slides 21 and 22 Parasites: Giardia (Slide 21) Here is a parasite that is spread by drinking contaminated water. Giardia lamblia lives in the intestines and can cause diarrhea and other intestinal problems. (Slide 22) Giardia infection is diagnosed by microscopically examining a slide preparation. When the medical laboratory scientist sees this parasite, a report is sent to the doctor so that the patient can receive the appropriate treatment for this disease. Slide 23 Conclusion Microbiology is just one of many fascinating and constantly changing areas of laboratory medicine. The medical laboratory scientist is a laboratory detective who provides the critical identification of not only microorganisms, but atypical blood cells and other abnormalities that are very important in the diagnosis and treatment of diseases. Although the medical laboratory is behind the scenes, the professionals who work in the lab—medical laboratory scientists, medical laboratory technicians, cytotechnologists, histologic technicians, phlebotomists, and pathologists—make a vital contribution to health care. The American Society for Clinical Pathology (ASCP) provides excellence in education, certification, and advocacy on behalf of patients, pathologists, and laboratory professionals. We welcome your comments on this presentation. You may contact us at: American Society for Clinical Pathology 33 W. Monroe St., Suite 1600 Chicago, IL 60603 Phone: 312-541-4999 Fax: 312-541-4998 Toll-free: 800-267-2727 Customer Service: [email protected] www.ascp.org 8