Clinical biochemistry - intro Flashcards

(33 cards)

1
Q

What 4 steps must be carried out before taking bloods?

A
  1. take the history
  2. perform a physical examination
  3. identify clinical problems
  4. formulate a differential diagnoses
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2
Q

What steps are taken following a differential diagnosis?

A
  • Tests to narrow down the list of possible diagnosis
  • Identify profile or pattern of changes
  • May need further specialist tests
  • Diagnosis
  • Treatment
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3
Q

Give some examples of screening tests

A
  • Urine sample
  • Radiography
  • Ultrasound
  • Biochemistry panel
  • Haematology
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4
Q

Define the term clinical biochemistry

A

The analysis of samples of body fluids for the purpose of diagnosis, treatment and prevention of disease

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5
Q

Which body fluids are most commonly used for analysis?

A

Serum
Plasma
Urine

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6
Q

What must be added to a plasma sample and why?

A

Anticoagulant to avoid clotting

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7
Q

What does plasma contain?

A

Proteins - albumin, globulin
Electrolytes
Water

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8
Q

What must be done to a serum sample?

A

Must be left and allowed to clot

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9
Q

Out of serum and plasma, which does not contain coagulation factors?

A

Serum

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10
Q

What are the functions of plasma?

A
Transport to and from tissues:
- Nutrients
- Hormones 
- Metabolites and vitamins
Blood clotting
Maintenance of osmolarity
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11
Q

What must plasma samples harvested from blood be kept in?

A

Lithium heparin tubes (anti-coagulant)

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12
Q

Plasma obtained from blood is placed in what kind of tube for a coagulation sample?

A

Sodium citrate - prevents the action of coagulation factors

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13
Q

What are the 3 waste products of plsama?

A
  • creatinine
  • urea
  • bilirubin
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14
Q

What tube must blood be placed in for a serum sample?

A

A glass tube

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15
Q

How is serum collected?

A
  1. place blood in a glass tube
  2. allow blood to clot
  3. centrifuge and separate supernatant
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16
Q

What is an alternative serum collecting method?

A

Plastic tubes with a serum activator and separation gel can be used - allows better separation from clot and cells

17
Q

If being sent to a lab plasma/serum should be collected into what type of tube?

A

NaFlouride/oxalate or EDTA tube = grey top

18
Q

What would you run tests for to assess kidney function?

A

Creatinine
Urea
Phosphate
USG

19
Q

What are the effects of decreased serum conc?

A
Decreased input:
- Decreased synthesis
- Nutritional deficiency
- Poor absorption
Increased output:
- Excessive demand
- Increased excretion
20
Q

What are the effects of increased serum conc?

A
Increased input:
- Increased synthesis
- Tissue damage and leakage from intracellular compartment
Decreased output:
- Decreased utilisation 
- Impaired excretion
21
Q

Where are reference interval values from?

A

The median 95% of a tested population of healthy animals

22
Q

What is standard devaition?

A

The spread of values around the mean

23
Q

How are normal and pathological ranges spread:

  1. ideally
  2. in reality
A
  • Ideally their ranges would be separated

- In reality there is often overlap providing a ‘grey area’

24
Q

What is the risk that comes with ‘over testing’

A

If many tests are performed on an individual animal the likelihood that a test result will come back as abnormal increases

25
Give some pre-analytical error examples
Sample collection, handling, submission Technique Tubes Timing
26
What are preanalytical errors caused by?
- Sample labelling and transcription errors - Inadequate anticoagulant - Sample contamination - Improper handling - Long or inappropriate storage
27
Give some examples of analytical errors
Due to test methodology - Not calibrated - Interfering substance - Test method performance
28
What are possible sources of analytical errors
- incorrect reporting of results - failure to calibrate refractometer - contamination of serum with EDTA - delayed separation of plasma/serum
29
Compare the definitions of accuracy and precision
``` Accuracy = how close the test result is to the 'true value' of the analyte Precision = the reproducibility of a laboratory method ```
30
Define the definitions of sensitivity and specificity
``` Sensitivity = the likelihood of a positive result when disease is present Specificity = the likelihood of a negative result when the disease is absent ```
31
Screening test must be very … | Confirmatory tests must be very ...
Sensitive as you do not want to miss any infected animals | Specific as we want to be sure than the positive animal really has the disease
32
Give definitions of positive and negative predictive values
``` PPV = the likelihood that a patient with a positive result has the disease NPV = the likelihood that a patient with a negative test does not has the disease ```
33
Which 3 factors affect PPV and NPV?
Specificity Sensitivity Prevalence of disease