1. Unit 18 Laboratory Assistant Skills

2. 18:1 Operating the Microscope
Many different models
Monocular microscopes – one eye piece
Binocular microscopes – two eye pieces
Quality varies
Calculation of magnification
Care and cleaning of microscope
Basic principles for operating a microscope
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Types of Microscopes
Compound, bright-field
Epiflourescence
Electron
Purpose: magnify or enlarge objects so they become more visible
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Parts of a Microscope
Base
Arm
Eyepieces or ocular viewpieces
Objectives
Revolving nosepiece
Stage
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5. Parts of a Microscope (continued)
Coarse adjustment
Fine adjustment
Iris diaphragm
Illuminating light
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6. 18:2 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
Use sterile applicator swab to collect specimen
Keep specimen moist and free from contact with anything else
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7. Obtaining and Handling Cultures (continued)
Direct smear or bacteriological smear
Agar plate, culture plate, petri dish, culture media tube
Culture and sensitivity
Resistant organisms
Sensitive organisms
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8. Obtaining and Handling Cultures (continued)
Fixing a slide
Gram’s stain
Standard precautions
Basic principles for obtaining a culture specimen
Basic principles for preparing a direct smear
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9. Obtaining and Handling Cultures (continued)
Basic principles for streaking an agar plate
Basic principles for transferring culture from agar plate to slide
Basic principles for staining with Gram’s stain
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10. 18:3 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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11. Methods of Obtaining Blood
Skin puncture
Venipuncture
Arterial blood
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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
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13. 18:4 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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14. 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
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15. 18:5 Measuring Hemoglobin
Used to determine oxygen-carrying capacity of the blood
Hemolysis
Hemoglobinometer
Automated photometer
Normal values
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16. Measuring Hemoglobin (continued)
Abnormal values
Accuracy is essential
Basic principles of using a hemoglobinometer
Basic principles of using a photometer
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18:6 Counting Blood Cells
Erythrocyte and leukocyte counts are done to determine the number of blood cells in the blood
Methods used
Hemacytometer counting chamber
Must dilute blood first
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18. Counting Blood Cells (continued)
Microscopic powers used
Normal values
Accuracy is essential
Basic principles for counting blood cells
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19. 18:7 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)
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20. Preparing and Staining a Blood Film or Smear (continued)
Basic principles for preparing
Basic principles for staining with Wright’s stain
Basic principles for staining with a quick stain kit
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21. 18:8 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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22. 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
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23. 18:9 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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24. Performing an ESR (continued)
Special rack used for ESR
Measurements usually taken at specific time periods
Normal values can vary slightly
Abnormal readings
Basic principles for performing erythrocyte sedimentation rate
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25. 18:10 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)
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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
Basic principles for measuring blood-sugar/glucose level
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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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18:11 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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30. Testing Urine (continued)
Volume
Color
Transparency
Odor
pH reaction
Specific gravity
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31. Testing Urine (continued)
Glucose
Albumin or protein
Acetones or ketones
Blood
Pus
Bacteria
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32. Testing Urine (continued)
Red blood cells (erythrocytes)
White blood cells (leukocytes)
Bilirubin
Urobilinogen
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Urinalysis
Examination of the urine
Includes physical, chemical, and microscopic testing
Physical examination usually done first
Chemical testing
Microscopic examination
Urine should be fresh – more accurate
Standard precautions
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34. 18:12 Using Reagent Strips to Test Urine
Commonly used for chemical testing of urine
Reagent strips
Storage of strips
Chemical reactants – note expiration
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35. Using Reagent Strips to Test Urine (continued)pH
Protein
Glucose
Ketone or acetone
Blood
Bilirubin
Urobilinogen
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36. Using Reagent Strips to Test Urine (continued)
Types of reagent strips
Automated strip readers or analyzers
Read instructions carefully
Fresh urine specimen should be used
Record results of test correctly
Basic principles of testing urine with reagent strips
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37. 18:13 Measuring Specific Gravity
Specific gravity defined
Low specific gravity of urine
High specific gravity of urine
Urinometer
Refractometer
Basic principles for measuring specific gravity
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38. 18:14 Preparing Urine for Microscopic Examination
Purpose
Fresh, first-voided morning specimen preferred
Only portion examined
Size of drop of concentrated urine examined is important
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39. Preparing Urine for Microscopic Examination (continued)
Urinary sediment should be examined immediately
Identification of substances present
Basic principles for preparing urine
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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
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