Laboratory Assistant Skills Chapter 19 Laboratory Assistant Skills

Career Highlights Medical laboratory assistants are important members of the health care field Education—usually requires specialized health occupation education training Licensed, registered, certified Knowledge and skills required

19:1 Operating the Microscope Many different models Monocular microscopes—one eye piece Binocular microscopes—two eye pieces Quality varies Calculation of magnification

Types of Microscopes Compound, bright-field Epifluorescence Electron Microscopes usually contain the same basic parts

Parts of a Microscope Base Arm Eyepiece(s) or ocular viewpiece Objectives Revolving nosepiece Stage (continues)

Parts of a Microscope (continued) Coarse adjustment Fine adjustment Iris diaphragm Illuminating light Body tube

19:2 Obtaining and Handling Cultures Obtained when doctor wants to identify the causative agent of a disease Sample specimen is either examined at that time or grown and then examined Sterile collection container and swab to collect the culture Container with proper medium (continues)

Obtaining and Handling Cultures (continued) Direct smear or bacteriological smear Agar plate, culture plate, petri dish, culture media tube Culture and sensitivity (C&S) Resistant organisms Sensitive organisms (continues)

Obtaining and Handling Cultures (continued) Fixing a slide Gram’s stain technique Gram positive Gram negative Rapid identification test kits Standard precautions

19:3 Puncturing the Skin to Obtain Capillary Blood Often used to assist physician in making a diagnosis Responsibility for obtaining blood for various blood test varies Check your state regulations Always know what you are permitted to do

Methods of Obtaining Blood Skin puncture Venipuncture Arterial blood

Skin Puncture Aseptic technique Common puncture sites Points to check prior to skin puncture Proper type of puncture Always remove first drop of blood After puncture specimen obtained Always use standard precautions

19:4 Performing a Microhematocrit Also called HCT or “crit” Measures volume of packed red blood cells (RBCs) or erythrocytes in the blood Often described as percentage of RBCs per volume of blood Different methods Microhematocrit centrifuge (continues)

Performing a Microhematocrit (continued) Capillary tubes Normal values Abnormal readings Accuracy is essential Careful recording of tests Physician’s responsibility to report test results to patient

19:5 Measuring Hemoglobin Hemoglobin (Hgb) determines oxygen-carrying capacity of the blood Hemolysis Hemoglobinometer Automated photometer Normal values Double check readings for accuracy

19:6 Preparing and Staining a Blood Film or Smear Preparation of blood film or smear Uses of blood film or smear Equipment must be extremely clean Wright’s stain Quick stain (three-step method)

19:7 Testing for Blood Types Blood types inherited from parents Type of blood determined by presence of certain factors called antigens on red blood cells Antigen ABO blood type system Rh type system (continues)

Testing for Blood Types (continued) Antigen-antibody reaction Typing and crossmatch Hemolytic disease of the newborn (HDN) Using anti-serums for blood typing Basic principles for testing for blood types with anti-serum

19:8 Performing an Erythrocyte Sedimentation Rate (ESR) Measures the distance that red blood cells have fallen or settled to the bottom of a glass test tube in a specific period of time Also called sedimentation rate or sed rate Basic procedure for test (continues)

Performing an ESR (continued) Special rack used for ESR Measurements usually taken at specific time periods Wintrobe or Westergren methods Normal values can vary slightly Abnormal readings

19:9 Measuring Blood-Sugar (Glucose) Level Glucose metabolism Diabetes mellitus Control of diabetes mellitus Fasting blood sugar (FBS) Glucose tolerance test (GTT) Glycohemoglobin test (HbA1C or HbA1)

Urine Tests Previously, diabetics used urine tests to check level of glucose High glucose in urine would indicate high glucose in blood Urine tests are not as accurate because kidney function varies between individuals Most diabetics use blood testing now

Blood Glucose Advantages of checking blood glucose versus urine glucose Testing blood with reagent strips Proper care of reagent strips Proper use and care of glucose meter Instructions to patients

Summary Different blood tests are used to diagnose disease Accuracy is essential with any test Standard precautions must be observed at all times

19:10 Testing Urine Often done to determine physical condition of patient Abnormal urine tests are often the first indication of disease Important to know normal and abnormal characteristics of urine (continues)

Testing Urine (continued) Physical testing of urine includes: Color Odor Transparency Specific gravity Physical characteristics normal/abnormal See Table 19-1 in text (continues)

Testing Urine (continued) Chemical testing of urine includes: Ph Protein Glucose Ketone Bilirubin Urobilinogen Blood (continues)

Testing Urine (continued) Microscopic testing of urine includes: Cells Crystals Amorphous deposits

Urinalysis Collection of urine in special containers Urine should be fresh—more accurate Examined within one hour or refrigerated Standard precautions

19:11 Using Reagent Strips to Test Urine Read manufacturer’s directions Reagent strips Storage of strips Chemical reactants—note expiration Strips are used to test for substances present in the urine (continues)

Using Reagent Strips to Test Urine (continued) Types of reagent strips used for testing Color comparison chart on bottle Quality control checks Automated strip readers—more accurate Record results of test correctly

19:12 Measuring Specific Gravity Specific gravity defined—measurement of concentration of urine Low specific gravity of urine High specific gravity of urine Measurement with a urinometer Measurement with a refractometer or digital refractometer

19:13 Preparing Urine for Microscopic Examination Purpose Fresh, first-voided morning specimen preferred—more concentrated Only portion examined Size of drop of concentrated urine examined is important (continues)

Preparing Urine for Microscopic Examination (continued) Urinary sediment should be examined immediately Identification of substances present See Fig. 19-43 in text Requires training and experience— must be qualified

Summary Substances present in urine are often first indication of disease Variety of urine tests performed to check for these substances Observe standard precautions while performing any urine tests