Diagnostic Tests (Catchpole)

Question 1

Dxx for IMHa

Answer 1

• COombs test

Question 2

What are spherocytes?

Answer 2

• Hbg dense small RBCs, indicates phagocytosis in spleen

- RBC coated in some kind of antigen

Question 3

When is in saline agglutination observed?

Answer 3

RBCs coated in Ab and complement

• when cooled outside the body they agglutinate
• in saline r/o artefact (Roulaeux) that can appear the same in whole blood

Question 4

Outline Coombs test

Answer 4

• patient sample with RBC coated in autoAb
• Coombs reagent (Anti-canine Ig Ab) added (and negative control saline)
  > + result RBCs remain as a shield across the whole well d/t cross linking by Coombs reagent
  > - result = button in the bottom of the well as all cells fall down
• usually polyclonal antiserum is added, some specialist places have monoclonal so can distinguish IgM, IgG and anti-C3 (complement)

Question 5

How do IgM and IgG based responses differ?

Answer 5

> IgM
- v potent complement activator
- lots of complement mediated destruction (INTRAVASCULAR)
IgG
- opsonin
- lots of macrophage destruction in spleen/liver (EXTRAVASCULAR)
- more likely to develop jaundice

Question 6

When else may agglutination be used?

Answer 6

> Blood typing and cross matching
- Mix RBC with Ag + anti-serum Ab
+ result = clumping
- want a negative result to show safe for transfusion

Question 7

Which test is used to r/o SLE?

Answer 7

ANA test (anti-nuclear antibody)

Question 8

What is SLE also known as?

Answer 8

= SLE like disease

= canine mulstisystemic immune-mediated dz

Question 9

Outline ANA test

Answer 9

1. cell line stuck to bottom of plate (any cells w/ a nucleus will do!)
2. patient serum (containing ANA) added
3. anti-canine IgG Ab with fluorescent tag added into dish
4. Observe under UV microscope
5. Repeated dilutions to still give a + result can be used to titre

Question 10

What test is used to r/o FAD?

Answer 10

• allercept serum assay ELISA (testing for a type 1 allergy)

Question 11

Outline allercept serum assay ELISA for FAD

Answer 11

1. flea antigen coats dish
2. add patient serum w/ IgE against flea Ag
3. FCE-R produced as recombinant protein with a little enzyme stuck on its head (FCE receptor comes from mast cell that would react in vivo)
4. substrate added - will change colour if the enzyme is present (and therefore if the IgE was present)

Question 12

What else is tested for in a similar way to IgE?

Answer 12

TG auto-ab tests

would expect TSH^ T4v if present