Flashcards in Testing in the diagnostic immunology laboratory Deck (9):
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
Is the ANA test sensitive and/or specific for SLE?
Sensitive but not specific
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.
Is the IgA tTg assay sensitive and/or specific for coeliacs?
BOTH sensitive and specific
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
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
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
Describe the test used to detect common variable immune deficiency (CVID)
- measure levels of IgG, IgA and IgM in the blood
- decrease in IgG and IgA indicates impaired antibody response