9 - Diagnosis of autoimmune diseases Flashcards
Sensitivity definition
Measure of how good is the test in identifying people with the disease
Specificity definition
Measure of how good is the test at correctly defining people without the disease
Positive predictive value
The proportion of people with a positive test who have the target disorder
Negative predictive value
The proportion of people with a negative test who do not have the target disorder
Type of autoimmune diagnostic tests
Non-specific = inflammatory markers
Disease specific = autoantibody testing, HLA typing
I have ignored the following slides
8-17
What is rheumatoid factor?
Antibody (IgM, G, A) directed against the Fc portion of IgG.
Commonly found in rheumatoid arthritis but not diagnostic of disease (70% sensitivity and specificity)
What does ACPA stand for?
Anti-CCP
What does ACPA do?
ACPA more specific for rheumatoid arthritis (95%) than rheumatoid factor
What does ANCA stand for?
Anti-neutrophilic cytoplasmic antibodies
What is ANCA specific for?
Wegener’s granulomatosis
Cytoplasmic ANCA vs perinuclear ANCA
Target antigens - 90% PR3 for cANCA; 70% MPO for pANCA
What is the usefulness of ANCA testing?
Positive ANCA is extremely useful for diagnosis
Histopathology remains gold standard for diagnosis
Reemergence of ANCA pos in a ANCA neg whilst in remission suggests a risk of disease flare however correlation is poor.
What signs would you see in autoimmune liver disease?
Anti-mitochondrial Ab specific for primary biliary sclerosis
Anti-smooth muscle Ab
What autoantibodies in DMT1?
Non-pathogenic
Several types: islet cell Ab, anti-GAD65, anti-insulinoma antigen 2, insulin autoantibodies
Disappear with progression of disease and destruction of B islet cells
