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Veterinary Diagnostics > Fundamentals Intro > Flashcards

Fundamentals Intro Flashcards

1
Q

What are all the diagnostic tests you could run?

A

Radiology, clinical pathology, biopsy, necropsy, histopathology, virology, bacteriology, toxicology, parasitology, serology and molecular diagnostics

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2
Q

How do you choose a diagnostic test?

A

Think about…
-Type of Sample
-Intended Use
-Is this a screening test or diagnostic
-Performance characteristics of said test

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3
Q

What is the difference between screening and diagnosis (antibody vs antigen)?

A

Screening - detect early disease or risk factors for disease in apparently healthy subjects (antibody)

Diagnosis - determine presence/absence of specific entity in symptomatic patient

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4
Q

What is sensitivity?

A

Measure’s ability of a test to correctly identify individuals with a condition (true positive rate)

Tp/ (TP + FP)

SnNout - high sensitivity = Negative test rules out disease

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5
Q

What is specificity?

A

Evaluates test capacity to accurately ID those without the condition (true negative)
TN / (TN + FP)
SpPIN - high specificity a positive rule in disease

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6
Q

What is positive predictive value?

A

It is precision, probability that a positive test result accurately indicates the presence of a specific condition or disease

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7
Q

If my test is very sensitive but not very specific what does that mean in relation to the results?

A

It means that if you get a positive you can assume it is Truely positive. If you get a negative result it could be a false negative.

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8
Q

What is reliability?

A

does the test give similar results under consistent testing conditions
-Over time
-When interpreted by different observers

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9
Q

What are some diagnostic testing methods?

A

Direct Exam: Electron microscopy, bacterial culture, antigen detection, molecular diagnostics (DNA/RNA and protien)
Indirect Exam: Virus Isolation
Serology: Antibody detection IgM and IgG

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10
Q

How do you visualize virus, parasites or bacteria?

A

Light Microscopy
Electron Microscopy

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11
Q

How do you detect proteins? (Antibody-antigen)

A

Elisa, IFA (immunofluorescence) and IHC(Immunohistochemistry)

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12
Q

How do you detect DNA or RNA?

A

PCR and NGS

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13
Q

What are some examples of pathogens that can be detected by electron microscopy?

A

PEDV, Poxvirus, E. Coli

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14
Q

How does Enzyme-linked immunosorbent Assay (ELIZA) work?

A

Antigen based (Antigen Capture)
-Detects pathogen itself
-Conjugated primary or secondary antibody
-Substrate gives a color reaction
Ex. Felv antigen test

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15
Q

How does Immunofluorescent antibody test (IFA) work?

A

-Cell culture or tissues
-Antibody has a fluorescent tag and is red with fluorescent microscope
-Need high viral titer

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16
Q

How does immunohistochemistry work?

A

-paraffin embedded tissues mounted on glass slides
-Sections are incubated with specific antibodies tagged with an enzyme
-Add substrate - if antigen of interest is in the tissues then color reacts
-Allows detection of the antigen in the lesion or specific cells

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17
Q

How can you use immunohistochemistry (IHC) in neoplasia cases?

A

Antibodies against tumor markers to detect cells of origin, stage differentiation and prognostic indicators

18
Q

How do molecular diagnostics work?

A

Qualitative or quantitative measure of:
-Genomic detection DNA/RNA - real time PCR, In situ hybridization, microarray, sequencing
-Proteins - flow cytometry, MALDI-TOF

19
Q

What components does a Realt time Polymerase Chain reaction (PCR) test need to be successful?

A

DNA primers and probes specific to target DNA, enough good quailty target DNA or RNA to amplify, validated test method, well-maintained equipment, limiting cross contamination

20
Q

What are the general steps to PCR?

A
  1. Increase Temp - denatures dna
  2. Annealing- attach primers and probes
    3.Polymerization and signal generaration - make new stands DNA, separate
21
Q

What is the ct value?

A

Cycle threshold - Cycle number at which the signal passes a fixed threshold

22
Q

Signal is proportional to the amount of amplified product. The higher the starting copy number of the target DNA in a sample the soon the signal increases in fluorescence. What does that mean in reference to CT value?

A

Low CT value (High viral load)

23
Q

What is key to remember about CT value?

A

Its not transferable, different among tests

24
Q

How can PCR be used in neoplasia cases?

A

-ID of clonal lymphocyte population
-Detect chromosonal translocation, deletions and duplications
-Detect c-kit mutation in mast cell tumor

25
Q

How does in-situ hybridization work?

A
  • In-situ = place of origin
    -Allows for visualization of a virus in the tissue or at the site of infection
    -Allows for determination of which virus is responsible for pathologic lesion
26
Q

What is next generation sequencing?

A

-Whole genome sequencing
-Can use to detect unknown viruses

There are portable sequencing options - MinION

27
Q

How does virus isolation work?

A

look for the effects of the virus (cytopathic effect) - see syncytial cells and inclusion bodies

28
Q

When are these tests most useful?

A

-ID cause of acute disease
-Determine cell origin of a neoplasm for prognosis or treatment

29
Q

How do you know you have found a pathogen on serology?

A

-Detection of antibodies
-4x increase in antibody titers between acute or convalescent stages of infection, detection IgM in primary infection

29
Q

Which antibody develops 1st? When does IgG get to the scene?

A

IgM (peak in 1 week then decrease)
IgG increase in 10-14 days

29
Q

How can you detect antibodies?

A

Serology, Elisa, Immunodiffusion and Virus Neutralization

30
Q

What is critical to think about when testing serology?

A

Think about the timing of your test relative to exposure

IgM without IgG may mean early exposure

31
Q

So Elisa can detect antigen, but can it detect antibodies too?

A

Yes!

32
Q

How does Elisa work?

A

-antibody based elisa
-dilutions allow for detecting antibody titers
-2nd antibody can detect IgM, IgA or IgG
Ex. Snap - FIV (antibodies) FelV (antigen)

33
Q

How does immunodiffusion work?

A

Antigen is loaded at center of gel, test serum is loaded on the periphery, a charge is added and antibodies move toward the antigen and precipitate making a band (positive)

34
Q

How does virus neutralization work?

A

-Antibodies in serum to inhibit virus replication
-titer inverse of highest dilution needed to neutralize
-highly specific
-slow or expensive b/c relies on inhibition of virus growth in cell culture

35
Q

What is the best way to determine what organisms are circulating in a population?

A

Serology

36
Q

What can produce antibodies?

A

Infection, exposure or vaccination

37
Q

What do antibody levels do after continuous exposure?

A

Decrease

38
Q

Why might a test not give you the results you expect?

A

Technical problem, early infection or recovery, false positive (low prevalence more false positives) , sequestering in tissues

Veterinary Diagnostics (13 decks)

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