Chapter 19
Laboratory Assistant Skills
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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
© 2009 Delmar, Cengage Learning
19:1 Operating the Microscope
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Many different models
Monocular microscopes—one eye piece
Binocular microscopes—two eye pieces
Quality varies
Calculation of magnification
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Types of Microscopes
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Compound, bright-field
Epifluorescence
Electron
Microscopes usually contain the same
basic parts
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Parts of a Microscope
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Base
Arm
Eyepiece(s) or ocular viewpiece
Objectives
Revolving nosepiece
Stage
(continues)
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Parts of a Microscope
(continued)
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Coarse adjustment
Fine adjustment
Iris diaphragm
Illuminating light
Body tube
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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)
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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
(continues)
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Obtaining and Handling Cultures
(continued)
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Fixing a slide
Gram’s stain technique
Gram positive
Gram negative
Rapid identification test kits
Standard precautions
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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
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Methods of Obtaining Blood
• Skin puncture
• Venipuncture
• Arterial blood
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Skin Puncture
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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
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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)
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Performing a Microhematocrit
(continued)
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Capillary tubes
Normal values
Abnormal readings
Accuracy is essential
Careful recording of tests
Physician’s responsibility to report
test results to patient
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19:5 Measuring Hemoglobin
• Hemoglobin (Hgb) determines
oxygen-carrying capacity of the blood
• Hemolysis
• Hemoglobinometer
• Automated photometer
• Normal values
• Double check readings for accuracy
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19:6 Preparing and Staining
a Blood Film or Smear
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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)
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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)
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Testing for Blood Types
(continued)
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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
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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)
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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
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19:9 Measuring Blood-Sugar
(Glucose) Level
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Glucose metabolism
Diabetes mellitus
Control of diabetes mellitus
Fasting blood sugar (FBS)
Glucose tolerance test (GTT)
Glycohemoglobin test (HbA1C or HbA1)
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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
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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
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Summary
• Different blood tests are used to
diagnose disease
• Accuracy is essential with any test
• Standard precautions must be observed
at all times
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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)
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Testing Urine
(continued)
• Physical testing of urine includes:
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Color
Odor
Transparency
Specific gravity
• Physical characteristics normal/abnormal
• See Table 19-1 in text
(continues)
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Testing Urine
(continued)
• Chemical testing of urine includes:
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Ph
Protein
Glucose
Ketone
Bilirubin
Urobilinogen
Blood
(continues)
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Testing Urine
(continued)
• Microscopic testing of urine includes:
– Cells
– Crystals
– Amorphous deposits
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Urinalysis
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Collection of urine in special containers
Urine should be fresh—more accurate
Examined within one hour or refrigerated
Standard precautions
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19:11 Using Reagent Strips
to Test Urine
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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)
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Using Reagent Strips to Test Urine
(continued)
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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
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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
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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)
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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
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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