Laboratory SA09 Flashcards
What samples are tests carried out on?
- Blood
- Urine
- Faeces
- Skin/hair
- Tissue/fluids
- Bacteriology
What laboratory analysers are commonly found in practice?
- Biochemistry
- Haematology
- Urine/Electrolyte
What rules must be followed when using laboratory analysers?
- Kept in secure position
- Kept at correct room temperature
- Used as per manufacturers instructions
- Be serviced regularly
- Quality control/assurance carried out
What is quality control?
- Check validity of test results
- Product from manufacturer to test QC
- Ensure analyser calibration is maintained
What is quality assurance?
- Extra steps to ensure reliable test results
- Ensure correct sample used for right test
- Right results reported to right person
- Correct recording of results
- Can send in-house test to external lab
What does a centrifuge do?
- Used to separate substances of different densities
- Sediment (denser) will settle at bottom
- Supernatant (lighter) remains at surface
What are the types of centrifuge?
- Swing out
- Angle head
- Micro haematocrit
What is a swing out centrifuge?
- Tubes placed in cups that turn horizontal when on
- Sediment packed uniformly against bottom of tube
- Sediment stays flat, supernatant easily removed
- High resistance to rotation generates heat
What is an angle head centrifuge?
- Tubes fixed at 25-40 degrees
- Sediment packs at bottom and sides of tube
- As head slows, sediment drops to bottom
- Sediment not packed tightly
- Can be run at higher speeds
What are electrolytes?
- Positive or negative ions in body fluid
- Sodium = NA+
- Potassium = K+
- Chloride = Cl-
What is a micro haematocrit centrifuge?
- Tubes held horizontally
- Allow for rapid sedimentation of small particles
- Can run at high speeds due to reduced resistance to rotation
What parts does a centrifuge have?
- Motor
- Drive shaft
- Rotor head
- Power switch
- Timer
- Speed control
- Tachometer
- Brake
- Most include protective shield
What is a tachometer?
- Indicates speed in revolutions per minute in centrifuges
What is important to remember when using a centrifuge?
- Use correct tubes
- Balance samples
- Use guard
- Centrifuges can move, position away from edge
- Correct speed and time for samples
Speeds + times
- Urine = 1500-2000rpm - 5 minutes
- Blood = 10,000rpm - 5 minutes
- F+ = 1000-1500rpm 3 minutes
What are the parts of a microscope?
- Eyepiece
- Rotating nose piece
- Arm
- Stage
- Objective lenses
- Slide clips
- Focus dial (Corse and fine)
- Sub-stage condenser
- Sub-stage condenser dial
- Light source
- Base
At what magnification are different items found on a microscope?
- Mites and worm eggs under low power (x4/8/10)
- Bacteria and blood cells under high power
(x40/100)
How should the x100 lens be used in a microscope?
- Drop of immersion oil onto slide below lens
- Adjust stage until lens tip in oil
- Adjust fine focus to sharpen image
How is the sub-stage condenser used on a microscope?
- Move sub-stage condenser up until just below stage
- If looking at transparent items (hair shafts) condenser can be lowered to darken object
How should a slide be viewed under a microscope?
Using the battlement technique
What equipment is needed for collecting a blood sample?
- Clippers
- Scrub/swab
- Syringe
- Needle
- Blood tubes
What is serum?
- Fluid collected from clotted blood once the clot has retracted
What is plasma?
- Fluid from non clotted blood
What is anticoagulant?
- A drug that prevents blood clotting
What are some commonly used anticoagulants?
- Heparin (Orange tube, biochem tests)
- EDTA (Ethylene Diamine Tetra-acetic Acid; Pink/red tube, heamatology tests)
- Fluoride oxalate (Yellow tube, glucose tests)
- Sodium citrate (Green/purple tube, clotting tests)
What are some possible problems with blood samples?
- Haemolysis
- Lipaemia
- Icteric
- Incorrect storage
- EDTA contamination
- Incomplete gel separation
Why does haemolysis happen to blood samples and how can it be prevented?
- Occurs when RBCs are broken/lysed
- RBCs then release contents into serum/plasma
- Excessive pressure on syringe, too vigorous mixing, using too small needle, freezing whole blood, not separating before transit
- Should use correct needle size and pressure, use small syringe, remove needle before decanting in tube, rotate, not shake, separate serum/plasma
How can lipaemia be prevented in blood sampled?
- Milky appearance due to fat cells in circulation
- Should starve patient before sample taken
What else can icteric blood samples mean other than liver issues?
- Jaundiced sample
- Can be due to haemolysis
How should blood samples be stored?
- Fill tubes immediately
- Fill EDTA first as most affected by clotting
- Test ASAP
- Refrigerate whole blood at 4 degrees for 5 days
- RBCs only stable for 24 hours
- Can freeze serum/plasma at -20 degrees
What is EDTA contamination?
- Caused by touching syringe against tube
- EDTA contains potassium
- Causes incorrect potassium readings
What equipment is is needed for a urine sample?
- Catheter?
- Syringe/needle?
- Collection bowl
- Sample pots
- Sterile universal container
What collection techniques can be used to get a urine sample?
- Catheterisation
- Cystocentesis
- Mid stream
- Manual expression
Care taken when placing a urinary catheter
- Must be aseptic
- Use sterile lube
- Do not introduce bacteria or contaminants
What is cystocentesis?
- Long needle into bladder
- Minimises contamination
- May get mild haemorrhage
Care taken when collecting mid stream urine sample
- Must not collect first part as contaminated from bacteria in urine tract
- Care to keep sample clean
Care taken with manual bladder expression
- Must be gentle
- Only done if no obstruction suspected
- May get mild haemorrhage
How should urine be stored?
- Plain pots; dry sterile universal container
- Good for microscopy, sediment, chemistries and specific gravity
- Boric acid; Red tube, contain preservative
- Good for microbiological culture
- Other preservatives; Thymol, Toulene
When should urine be tested?
- Test urine ASAP
- Cooled urine in fridge stops bacteria multiplying
- Crystals will still form
What is blood bichemistry?
- Levels of chemicals in the body
- Bio chemicals suspended in plasma/serum
- Used to check body functions and organs
How can blood be tested for biochemistry?
- Biochemistry analyser
- Testing sticks
- Glucometers
Why is it important to prevent haemolysis of blood samples when running biochemistry tests?
- Mild haemolysis shouldn’t cause problems
- Severe haemolysis affects filter
- Gives inaccurate results
- Can give false increased bilirubin from haemoglobin leaks
What is hyperkalaemia?
- Increased potassium (K)
- Leads to bradycardia + cardiac arrhythmia
- False positive results from EDTA contamination
Why is medical history important when testing blood?
- Exercise or starving can affect results
- Correct times post medications are important for some tests
What are the important functions of the liver?
- Glucose, protein, lipid synthesis
- Bile formation
- Vitamin and iron storage
- Detoxification
How can liver disease be caused?
- Infectious - viral, bacterial, parasitic
- Inflammatory (hepatitis)
- Toxin related
- Neoplastic
How can biochemistry results be used to diagnose liver disease?
- Damaged liver leaks enzymes into blood in larger amounts than usual
- These enzymes can be released from other areas
- Full blood biochemistry is required for diagnosis
How are carbohydrates digested and stored?
- Complex carbohydrates converted to monosaccaride glucose
- Liver stored glucose as a polysaccaride glycogen
How are proteins broken down?
- Proteins to amino acids
- Amino acids to amonia
- Amonia to urea
What is ALT?
- Serum alanine aminotransferase
- Found in hepatocyte cytoplasm
- Also released from kidneys, cardiac and skeletal muscle
- Increased levels indicate renal failure, cardiac disease, skeletal muscle damage and liver disease
What is AST?
- ## Serum aspirate aminotransferase
What is choleostasis?
Blocked bile duct
What is azotaemia?
Increased urea and creatinine in blood biochemistry
