© 2009 Delmar, Cengage Learning Chapter 19 Laboratory Assistant Skills.

© 2009 Delmar, Cengage Learning

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

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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

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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

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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

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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

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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

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Testing Urine(continued)

• Physical testing of urine includes:– Color

– Odor

– Transparency

– Specific gravity

• Physical characteristics normal/abnormal

• See Table 19-1 in text

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• Chemical testing of urine includes:– Ph

– Protein

– Glucose

– Ketone

– Bilirubin

– Urobilinogen

– Blood

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• 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 Stripsto 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

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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 forMicroscopic Examination

• Purpose

• Fresh, first-voided morning specimen preferred—more concentrated

• Only portion examined

• Size of drop of concentrated urine examined is important

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Preparing Urine forMicroscopic Examination

(continued)

• Urinary sediment should be examined immediately

• Identification of substances presentSee 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

© 2009 Delmar, Cengage Learning Chapter 19 Laboratory Assistant Skills.

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Transcript of © 2009 Delmar, Cengage Learning Chapter 19 Laboratory Assistant Skills.