Diagnostic Testing

Question 1

What is a diagnostic test?

Answer 1

Generic term for any procedure to categorize the nature or severity of a condition

• procedure to classify a thing as “normal” or “not normal” or further classify as to origin or severity
• ex: CBC, chemistry, HW test, ear cytology, etc

Question 2

Serology typically refers to the ______

Answer 2

Assessment of serum antibody concentration

- a measure of immune response to exposure

Question 3

Titer

Answer 3

Dilution of the serum until a desired antibody gets so low that it is undetected

• the last dilution is known as the “ highest” dilution
• 1:1 = 1 part serum, 1 part diluent

Question 4

If you conduct a test on each dilution, you can determine the last dilution at which an ______

Answer 4

Ag:Ab reaction occurs

- this is the endpoint titer

Question 5

The critical titer

Answer 5

Point where the animal is determined to be seropositive for the disease
- lab dependent, each lab has a different critical titer they consider to be “positive”

Question 6

You need to be _____ the critical titer to be classified as positive

Answer 6

Over

Question 7

What happens when the titer at week 1 and the titer at week 4 is only different by 1 dilution (2 fold increase)?

Answer 7

Considered within laboratory error and is not significant

Question 8

A ____ increase is considered to be greater than lab error

Answer 8

4 fold increase

• reflects active Ig production
• is diagnostic!

Question 9

Dilution of the endpoint titer

Answer 9

Equal to the log base 2 of the reciprocal titer

Question 10

In assessing a group, endpoint titers display an ________ between dilutions

Answer 10

Exponential increase

- use log2 transformation (the dilution number) to allow use of means as a measure of central tendency

Question 11

When are titer graphs useful?

Answer 11

• done to evaluate immune response to vaccination
• way to monitor exposures in a herd (if titers are low, then exposures are low in the herd)
• common to do in swine