Testing in the diagnostic immunology laboratory Flashcards Preview

Pathology-IMED4111 > Testing in the diagnostic immunology laboratory > Flashcards

Flashcards in Testing in the diagnostic immunology laboratory Deck (9):
1

Describe the test used to detect (SLE) Systemic Lupus Erythematosus

Anti-nuclear antibody (ANA) test
- SLE is an auto-immune disease
- ALA tests for anti-nuclear antibodies in the blood, which are antibodies against the person's own DNA
- general summary: antigen --> mix with serum containing antibody --> add 2nd detection antibody
- if the sample contains self-antibodies, they will bind to the cell nucleus
- a 2nd antibody is added to the sample, which binds to the auto-antibody and appears fluorescent
- homogenous fluorescence in the nucleus indicates SLE

2

Is the ANA test sensitive and/or specific for SLE?

Sensitive but not specific

3

Describe the tests used to detect Coeliac Disease

1) Assay of auto-antibodies to tissue transglutaminase (IgA tTG)
(similar to ANA test)
Auto antibodies tagged with an enzyme bind to cells, unbound antibiotics are washed away, enzyme causes colour change, indicates auto-antibodies.

2) HLA test
HLA DQ2 and DQ8 are genetic tests for the DQ2 and DQ8 alleles - almost all coeliacs have the allele. Also can be common in general population so it is used to rule out the disease.

4

Is the IgA tTg assay sensitive and/or specific for coeliacs?

BOTH sensitive and specific

5

Is the HLA test sensitive and/or specific for coeliacs?

Sensitive, not specific - used to rule OUT (SnOUT) - a sensitive test with a negative result means you're very unlikely to have it

6

Describe the tests used to detect allergy

1) Allergen-specific IgE levels
(Similar to ANA tests)
- antigen --> mix with serum containing antibody --> add 2nd detection antibody

2) Skin test
- skin prick to test immune response

7

When would you use allergen-specific IgE levels rather than skin test?

- recent antihistamine use
- patients on beta blockers (risk of anaphylaxis
- young children
- persistant severe/ unstable asthma
- history of anaphylaxis

8

Describe the test used to detect common variable immune deficiency (CVID)

Immunoglobulin measurement
- measure levels of IgG, IgA and IgM in the blood
- decrease in IgG and IgA indicates impaired antibody response

9

Describe the tests used to detect HIV

1) Western blot
- measures antibodies against HIV in the blood, which is an indication of the viral load
- similar to ANA and allergen specific IgE tests
- enzyme tagged antibodies bound to HIV are detected

2) Flow cytometry
- counts B and T cells in blood
- similar to above: antigen mixed with serum containing antibodies against lymphocytes, enzyme detects bound antibodies
- different in that it involves lasers
- CD4+ T cell count

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