1. Laboratory Assistant Skills
Chapter 19
Laboratory Assistant Skills

2. 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

3. 19:1 Operating the Microscope
Many different models
Monocular microscopes—one eye piece
Binocular microscopes—two eye pieces
Quality varies
Calculation of magnification

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

5. Parts of a Microscope Base Arm Eyepiece(s) or ocular viewpiece
Objectives
Revolving nosepiece
Stage
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6. Parts of a Microscope (continued)
Coarse adjustment
Fine adjustment
Iris diaphragm
Illuminating light
Body tube

7. 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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8. 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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9. Obtaining and Handling Cultures (continued)
Fixing a slide
Gram’s stain technique
Gram positive
Gram negative
Rapid identification test kits
Standard precautions

10. 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

11. Methods of Obtaining Blood
Skin puncture
Venipuncture
Arterial blood

12. 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

13. 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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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

15. 19:5 Measuring Hemoglobin
Hemoglobin (Hgb) determines oxygen-carrying capacity of the blood
Hemolysis
Hemoglobinometer
Automated photometer
Normal values
Double check readings for accuracy

16. 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)

17. 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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18. 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. 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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20. 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

21. 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)

22. 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

23. 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

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

25. 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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26. 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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27. Testing Urine (continued)
Chemical testing of urine includes: Ph
Protein
Glucose
Ketone
Bilirubin
Urobilinogen
Blood
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28. Testing Urine (continued)
Microscopic testing of urine includes:
Cells
Crystals
Amorphous deposits

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

30. 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
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31. 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

32. 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

33. 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
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34. Preparing Urine for Microscopic Examination (continued)
Urinary sediment should be examined immediately
Identification of substances present See Fig in text
Requires training and experience— must be qualified

35. 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