Diagnostics: Serology and Immunohistochemical

Question 1

Pathognomonic signs

Answer 1

Diagnostic sign marking the presence of a particular disease

Question 2

Silver dollar plaques on a horse indicate…

Answer 2

Dourine: Chronic veneral disease

Trypanosomoma equiperdum

Question 3

Pink diamond-shaped skin lesions in pigs indicate…

Answer 3

Swine erysipelas: diamond skin disease

Erysipelothrix rhusiopathiae

Question 4

Types of specimens for collection

Answer 4

Tissues
Blood
Scrapes/Swabs/Impression
Transudate/Exudates
Urine/misc fluids
Feces
Vomit/sputum
Blood

Question 5

Factors that influence specimen collection choice

Answer 5

Clinical symptoms
Duration of infection
Diagnostic tests to be performed

Question 6

What is the first step in accurate diagnostic testing?

Answer 6

Proper specimen collection!

Question 7

Specimens for BACTERIAL infections

Answer 7

Dog/Cat: skin scrape, hair, ear swab, urine, blood, wound swabs

Horses: nasal swabs and fluids, wound swabs

Food animals: Post mortem tissues/organs, milk

Question 8

Specimens for PARASITIC infections

*base on parasitic life cycle

Answer 8

Feces
Vomit
Sputum
Blood
Urine
Skin scrape
Muscle biopsy
Post mortem samples

Question 9

Specimens for VIRAL infections

Answer 9

Feces
Blood
Nasal, tracheal, eye swabs
Sputum
Post mortem samples

Question 10

At what phase of disease is the best time to collect samples?

Answer 10

During the acute phase

Question 11

Goals of aseptic sampling

Answer 11

Reduce/avoid contamination with normal flora

Avoid environmental contamination

Reduce risk of secondary infection

Question 12

Correct handling and transport depends on…

Answer 12

Pathogen type
Specimen type
Diagnostic tests being performed

Question 13

3 types of diagnostic tests

Answer 13

Phenotypic
Molecular
Serology/immunohistochemical

Question 14

What do immunohistochemical tests detect?

Answer 14

Pathogen-specific antibodies or antigens

Question 15

Why choose immunohistochemical methods?

Answer 15

Quickly diagnose threatening agents

Organisms take too long to culture (mycobac)

Organisms are difficult to culture (Rickettsiae)

Unculturable organisms (Clostridium piliformis)

Question 16

The ability of the test to detect very minute quantities of antigen or antibody

Answer 16

Sensitivity

Question 17

The ability of the test to detect reactions between homologous Ag and Ab, minimizing false positives

Answer 17

Specificity

Question 18

What specimens detect antibodies?

Answer 18

Blood, tissue fluids

serology

Question 19

What specimens detect antigens?

Answer 19

Areas of infection where pathogens replicate and are present

serotyping

Question 20

Best time to collect to detect antigen

Answer 20

Acute phase

Question 21

Best time to collect to detect antibody

Answer 21

10-14 days after infection

Question 22

Indicators for active or recent infection

Answer 22

Pathogen detection

Clinical symptoms

Antibody titer
*number of circulating antibodies will decrease over time. Presence may not indicate active infection. Absence may not mean absence of pathogen

Question 23

What test detects Ab response to viruses, parasites, bacteria or fungi?

Answer 23

ELISA (Enzyme Linked ImmunoSorbent Assay)

Question 24

Benefits of ELISA

Answer 24

High sensitivity and specificity

Quantitative: indicates amount of Ag or Ab present

Question 25

Types of ELISA

Answer 25

Direct
Indirect
Sandwich
Lateral-flow
IDEXX snap test

Question 26

In which type of ELISA is the antigen bound to the solid phase, washed, then directly incubated with conjugated antibody?

Answer 26

Direct

Question 27

Features of DIRECT ELISA

Answer 27

qualitative or quantitative Ag detection

antibody screening

epitope mapping

Question 28

What makes INDIRECT ELISA more sensitive than direct ELISA?

Answer 28

Addition of labeled second antibody enhances the signal of the primary antibody

Question 29

What type of ELISA was designed for soluble antigens or low concentrations, and requires a compatible antibody pair that recognizes different epitopes on the same antigen?

Answer 29

Sandwich

Question 30

Variation of ELISA that is mostly qualitative or semi-quantitative and confirms presence or absence of target molecule

Answer 30

Lateral-Flow Immunoassay

Question 31

Benefits of lateral flow immunoassay

Answer 31

User friendly
One-step analysis
Low cost
Versatile
Rapid

Question 32

What is a variation of the lateral flow tests that uses bidirectional flow and integrates a wash step to minimize false positives?

Answer 32

IDEXX snap tests

Question 33

Benefits of IDEXX snap tests

Answer 33

Integrated wash step
Increased sensitivity
Small amount of antigen will work
Variety of tests
Some tests detect multiple diseases

Question 34

Benefits of Immunofluorescence

Answer 34

Localize pathogen

Detect autoimmune, viral, diseases (HW, FIP)

High sensitivity and specificity

Question 35

What test employs a visible clumping of particulate Ag with its specific Ab, forming a visible lattice?

Answer 35

Agglutination test

Question 36

Benefits of agglutination

Answer 36

Easy to make
Easy to use
Cheap
Clearly visible reaction

Question 37

Disadvantages of agglutination

Answer 37

Low sensitivity
Low specificity
Affected by vaccine-induced Ab

Question 38

Benefits of immunochemical methods

Answer 38

Good for non-culturables
Most have high sensitivity
Most have high specificity
Mid to high volume testing possible
Indication of immune response

Question 39

Disadvantages of immunochemical methods

Answer 39

Detection of Ab not always indicative of active infection

Detection limit: Ab might not be detected in samples taken early in infection

Ab can reflect multiple pathogens that have the same antigen