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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
What do reference intervals represent?
RI represents typical values seen in 95% of healthy animals
26
How many healthy animals will fall below the RI? Above? Outside?
* 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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Are results within the reference interval range considered to be normal? Explain why or why not?
* 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)!
29
How can errors in laboratory results occur?
* Errors: instrument/analyzer, reagents, or operator
30
A pre-analytical error is a result in?
Pre-analytical error: collection of the sample
31
An analytical error is a result in?
Analytical error: testing the sample
32
A post-analytical error is a result in?
Post-analytical error: typically human error in reporting results
33
Quality control programs involve? What does this program consist of?
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
Quality Control * Test Precision = same result with multiple runs? * Tightly clustered = good precision * Can be precise, but inaccurate * Accuracy – mathematical average = true value?
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41
What information can be used to refine your differential diagnosis list OR be diagnostic?
Signalment, history, physical exam, & lab data
42
Values ________ the RI may be more significant.
outside
43
Azotemia + a urine specific gravity indicating that animal is not concentrating urine = ________ disease
renal
44
Azotemia + concentrated urine = ?
dehydration
45
Stress leukogram = ?
glucocorticoid (cortisol/prednisone)
46
What is the first component of a hematology evaluation?
Complete Blood Count (CBC)
47
Where is blood collected from on an animal? What needle gauge(s) are typically used? Where are the veins located?
* 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
When you want to send out a CBC to the lab, what tube do you put your blood sample into?
A purple top tube which contains anticoagulant.
49
The anticoagulant in a purple top tube is made up of?
Sodium or potassium EDTA
50
What is the function of Sodium or potassium EDTA?
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
What do automated instruments (hematology analyzers) measure?
* 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
What does the refractometer measure?
Plasma protein
53
What does heat precipitation/other methods measure?
Fibrinogen
54
How do automated hematology analyzers measure the hemoglobin concentration? Explain step by step.
* 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
What is the internal quality control check when using an automated hematology analyzer?
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
What values do you obtain when using an automated hematology analyzer?
* 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
Describe the electrical impedance (Coulter technology) method for cell counting and sizing?
58
59
Describe the flow cytometry method for cell counting and sizing?
more detail re: differentials
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62
How do you obtain a PCV?
* 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
Label this image accordingly.
64
The PCV should match closely with?
PCV should match closely (within 3%) with hematocrit generated by the hematology analyzer
65
How do you measure plasma protein concentration?
* Performed on a spun microhematocrit tube * Tube is broken between plasma and buffy coat * Portion of plasma is placed on refractometer glass
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5.5
67
Blood smears should always be made to?
corroborate CBC findings. Also allows ID of infectious organisms and neoplastic cells. Disease causing agents will alter results --> be mindful of this.
68
Describe the blood smear procedure.
* 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
What makes up a proper blood smear?
* A properly made blood smear has 3 main components: * 1. Feathered edge * 2. Monolayer (cell counting area) * 3. Body
70
Label this blood smear image accordingly.
71
Blood smear staining is similar to which staining properties?
Similar staining properties to hematoxylin & eosin on histologic specimens
72
Eosin dye is defined as?
Eosin – acidic dye that stains basic structures red (e.g., red blood cells, eosinophil granules)
73
Azure dye is defined as?
Azure dye – basic dye that stains acidic structures purple (e.g., nuclei of cells)
74
Aqueous Romanowsky is?
* Diff Quik * Commonly used in clinics
75
Methanolic Romanowsky is?
* Wright-Giemsa * Commonly used in reference laboratories – a clinical pathologist favorite

Clinical Pathology (31 decks)

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