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Clinical Pathology > Week 1 - Intro > Flashcards

Week 1 - Intro Flashcards

1
Q

What is the definition of clinical pathology?

A

Clinical pathology is the study of disease in the clinical environment by use of laboratory assays.

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2
Q

Clinical pathology = ?

A

Pattern recognition.

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3
Q
  1. What are some examples of hematology?
  2. What are some examples of clinical chemistry?
A
    • Complete blood count (CBC)
      * Blood smear examination
    • Biochemistry profile

Coagulation tests
Blood gas analysis
Endocrinology

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4
Q

What should a validity test measure?

A

A valid test should measure the parameter (“analyte”) of interest over a range of values with minimal interferences.

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5
Q

An abnormal value of an analyte should have ?

A

a strong association with a disease or condition.
* Few false positive and few false negative results
* Important to establish medical decision limit (cut-off)
value

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6
Q

No laboratory test is _________, and ________ tests are often used in combination to ______ or __________ a disease

A

perfect, several, diagnose, categorize

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7
Q

Test Sensitivity and Specificity both depend on?

A

the prevalence of a
disease

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8
Q

True or False: NO test has 100% sensitivity and 100% specificity.

A

True
There is always a margin of error.

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9
Q

Define test sensitivity.

A

Sensitivity = ability of a test to detect patients who
truly have a disease (true positives, or TP).

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10
Q

What does a test exhibiting high sensitivity mean?

A
  • Higher sensitivity = a diseased patient is more likely to test positive
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11
Q

If sensitivity of PCR for lymphoma = 91% what does that mean?

A
  • Tested in 100 animals with lymphoma:
  • 91% have positive result
  • 9% have false negative result
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12
Q

What is important in regards to sensitivity for screening tests?

A

Important to have high sensitivity for a screening test
* A negative result of a highly sensitive test effectively rules out a disease

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13
Q

Tests with high sensitivity are best used for ?

A

ruling OUT a disease (“SnOUT”)

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14
Q

Define test specificity.

A

Specificity = ability of a test to detect patients that
truly do not have a disease (true negatives, or TN)

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15
Q

What does a test exhibiting high specificity mean?

A

Higher specificity means a non-diseased patient is more likely to test negative

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16
Q

If test specificity is 95%, then out of 100 animals
without the disease?

A
  • 95% of animals will have a negative test result
  • 5% of animals will have false positive results
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17
Q

What is important in regards to specificity for confirmatory tests?

A

Important to have high specificity for a confirmatory test
* Few non-diseased patients will incorrectly test positive (false positive)

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18
Q

Test with High Specificity are best for?

A

ruling in a disease (“SpIN”)
aka In other words, good for confirming a diagnosis

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19
Q

Sensitive test: when negative result?

A

rules OUT the disease

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20
Q

Specific test when positive result?

A

rules IN the disease

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21
Q

Reference intervals
How do we know what values are normal?

A

Each lab should have its own RI for each species
Each lab should have its own RI (especially based on state, country, etc).

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22
Q

What can be seen below?

A

Reference interval chart.

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23
Q

Reference Intervals (RI) are established from how many samples?

A

preferably 60, and ideally 120 samples

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24
Q

In regards to reference intervals, data are?

A

analyzed and typically fit a normal (Gaussian)
distribution

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25
Q

What do reference intervals represent?

A

RI represents typical values seen in 95% of healthy animals

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26
Q

How many healthy animals will fall below the RI? Above? Outside?

A
  • 2.5% of healthy animals will be below the RI, and
    2.5% of healthy animals above the RI
  • 1/20 healthy animals will have a result outside of
    the RI
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27
Q
A
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28
Q

Are results within the reference interval range considered to be normal? Explain why or why not?

A
  • Result within the reference interval (WRI), it is not
    necessarily “normal”
  • May not be normal for a given disease process
  • Common to have 2 disease processes/pathologic states
    “pushing” and “pulling” the result to be within the
    reference interval
  • Do NOT overlook values that aren’t flagged as high
    (H) or low (L)!
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29
Q

How can errors in laboratory results occur?

A
  • Errors: instrument/analyzer, reagents, or operator
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30
Q

A pre-analytical error is a result in?

A

Pre-analytical error: collection of the sample

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31
Q

An analytical error is a result in?

A

Analytical error: testing the sample

32
Q

A post-analytical error is a result in?

A

Post-analytical error: typically human error in reporting results

33
Q

Quality control programs involve? What does this program consist of?

A

Involves analyzing quality control materials (QCM) that
have pre-determined concentrations of an analyte
* Typically 3 levels (low, normal, high)
* Each laboratory establishes its allowable error

34
Q

Quality Control
* Test Precision = same result with multiple
runs?
* Tightly clustered = good precision
* Can be precise, but inaccurate
* Accuracy – mathematical average = true
value?

A
35
Q
A
36
Q
A
37
Q
A
38
Q
A
39
Q
A
40
Q
A
41
Q

What information can be used to refine your differential diagnosis list OR be diagnostic?

A

Signalment, history, physical exam, & lab data

42
Q

Values ________ the RI may be more significant.

A

outside

43
Q

Azotemia + a urine specific gravity indicating that animal is not concentrating urine = ________ disease

A

renal

44
Q

Azotemia + concentrated urine = ?

A

dehydration

45
Q

Stress leukogram = ?

A

glucocorticoid (cortisol/prednisone)

46
Q

What is the first component of a hematology evaluation?

A

Complete Blood Count (CBC)

47
Q

Where is blood collected from on an animal?
What needle gauge(s) are typically used?
Where are the veins located?

A
  • Blood is collected from:
  • Jugular vein
  • Cephalic vein
  • Saphenous vein
  • values from the artery are different.
  • lateral in dogs, medial in cats
  • 18- to 22-gauge needle in
    small animals
48
Q

When you want to send out a CBC to the lab, what tube do you put your blood sample into?

A

A purple top tube which contains anticoagulant.

49
Q

The anticoagulant in a purple top tube is made up of?

A

Sodium or potassium EDTA

50
Q

What is the function of Sodium or potassium EDTA?

A

Function: chelates calcium and other divalent cations to inhibit
the coagulation cascade –> plasma, not serum
* What’s the difference?
- Plasma contains clotting factors
- Serum does not contain clotting factors

51
Q

What do automated instruments (hematology analyzers) measure?

A
  • Automated instruments (hematology analyzers)
  • White blood cells (WBC): Total WBC count, neutrophils, basophils, eosinophils, monocytes, lymphocytes
  • Red blood cells (RBC): RBC count, hemoglobin, hematocrit, MCHC, MCH, MCV, +/- reticulocyte count
  • Platelets: Platelet count
52
Q

What does the refractometer measure?

A

Plasma protein

53
Q

What does heat precipitation/other methods measure?

A

Fibrinogen

54
Q

How do automated hematology analyzers measure the hemoglobin concentration? Explain step by step.

A
  • Use spectrophotometry to determine hemoglobin
    concentration
  • The blood sample is aspirated into the analyzer –> chemical agent is added to lyse cells which liberates
    hemoglobin
  • Absorbance of light at a specific wavelength is
    proportional to concentration of hemoglobin.
55
Q

What is the internal quality control check when using an automated hematology analyzer?

A

General rule as an internal quality control check:
hemoglobin is 1/3 of hematocrit value
* E.g. If hematocrit is 33%, hemoglobin concentration
should be ~11 g/dL

56
Q

What values do you obtain when using an automated hematology analyzer?

A
  • Mean cell hemoglobin (MCH)
  • Mean cell hemoglobin concentration (MCHC)
  • Calculated from hemoglobin concentration and
    hematocrit
  • Provides an index for quantity of hemoglobin relative to
    volume of packed RBCs:
  • Hgb (g/dL)/PCV (%) * 100 = MCHC (g/dL)
57
Q

Describe the electrical impedance (Coulter technology) method for cell counting and sizing?

A
58
Q
A
59
Q

Describe the flow cytometry method for cell counting and sizing?

A

more detail re: differentials

60
Q
A
61
Q
A
62
Q

How do you obtain a PCV?

A
  • Portion of EDTA whole blood is pulled
    into a microhematocrit tube, sealed,
    and centrifuged at high speed
  • After spinning, left with 3 fractions:
  • Plasma
  • Buffy coat = WBCs, Platelets
  • Packed erythrocytes
63
Q

Label this image accordingly.

A
64
Q

The PCV should match closely with?

A

PCV should match closely (within 3%) with
hematocrit generated by the hematology analyzer

65
Q

How do you measure plasma protein concentration?

A
  • Performed on a spun microhematocrit tube
  • Tube is broken between plasma and buffy coat
  • Portion of plasma is placed on refractometer glass
66
Q
A

5.5

67
Q

Blood smears should always be made to?

A

corroborate CBC findings.
Also allows ID of infectious organisms and neoplastic
cells. Disease causing agents will alter results –> be mindful of this.

68
Q

Describe the blood smear procedure.

A
  • Procedure:
  • Use microhematocrit tube to apply drop of blood at frosted edge of glass slide
  • Hold spreader slide at a 30 degree angle
  • Pull back spreader slide until the blood wicks across
  • Rapidly and lightly push the spreader slide to make a smear
69
Q

What makes up a proper blood smear?

A
  • A properly made blood smear has 3 main
    components:
    1. Feathered edge
    1. Monolayer (cell counting area)
    1. Body
70
Q

Label this blood smear image accordingly.

A
71
Q

Blood smear staining is similar to which staining properties?

A

Similar staining properties to hematoxylin & eosin on
histologic specimens

72
Q

Eosin dye is defined as?

A

Eosin – acidic dye that stains basic structures red (e.g., red blood cells, eosinophil granules)

73
Q

Azure dye is defined as?

A

Azure dye – basic dye that stains acidic structures purple (e.g., nuclei of cells)

74
Q

Aqueous Romanowsky is?

A
  • Diff Quik
  • Commonly used in clinics
75
Q

Methanolic Romanowsky is?

A
  • Wright-Giemsa
  • Commonly used in reference laboratories – a clinical pathologist favorite

Clinical Pathology (31 decks)

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