Theme 2 Lecture 8: Diagnosis of autoimmune diseases Flashcards
What is autoimmune disease?
when the immune system dosen’t tolerate self antigens and identifies them as something that needs to be attacked
“antibodies against self”
How would we work out which autoimmune disease a patient has?
- take a history
- examine patient
- perform blood test (we have tests to detect which autoantibodies are present in patients blood)
What is your diagnosis?
- 51 yr old lady
- 18 month history of SOB
- pulmonary fibrosis
- fatigues, aches, pains
- thickening of skin on hands and changes in the skin around mouth
- sclerodactyly both hands
- livedo reticularis on the legs
- cool feet on palpitation
scleroderma
What is sclerodactyly?
hardening of the skin of the hand that causes the fingers to curl inward and take on a claw-like shape
What tests could you give to diagnose an autoimmune condition?
- ANA
- ANCA
- CK
- rheumatoid factor
- anti-CCP antibody
- complement
- FBC
- U&Es
- LFTs
- CRP
What is an ANA test?
- looks for antinuclear antibodies in your blood
- if test is +ve, could have an autoimmune disorder
What is the ANCA test used for?
to diagnose autoimmune vasculitis
What would an abnormal CK blood result indicate?
muscle damage (ck=creatine kinase)
What are the two tests that could potentially diagnose RA?
- rheumatoid factor (autoantibody in RA)
- anti-CCP antibody
What does FBC and LFTs stand for?
FBC - Full blood count
LFTs- liver function test
What is test specificity?
measure of how good the test is at correctly defining people without the disease
What is test sensitivity?
measure of how good the test is in identifying people with the disease
What is a positive predictive value?
proportion of people with a positive test who have the disorder
What is a negative predictive value?
proportion of people with a negative test who do not have the target disorder
What are the non-specific markers of inflammation? (e.g do not tell you which specific condition)
- ESR (erythrocyte sedimentation test)
- CRP
- ferritin
- fibrinogen
- haptoglobin
- albumin
- complement
What are antinuclear antibodies (ANA)?
Antibodies in the patient’s blood that bind to the cell nucleus
How does antinuclear antibody testing work?
- see if antibodies bind
- ANA immunoflourescence is always hep2
- if patient’s antibodies bind to antigen, colour appears
- different patterns for different antibodies
- +ve result may mean you have an autoimmune disorder
- different types of antibody are associated with different autoimmune diseases
Case 2: -25 yr old lady -presents to rheumatology clinic with 3 month history -patchy alopecia -painful and swollen joints of the hands -mouth ulcers -low platelet count -high creatinine -positive ANA screen What is diagnosis?
SLE
If you have a +ve ANA score, what could the diagnosis be?
- SLE
- RA
- Scleroderma
- Sjogren’s syndrome
What is rheumatoid factor?
- antibody directed against the Fc portion of IgG
- commonly found in RA but not diagnostic of disease
- can be seen with other disorders in which polyclonal stimulation of B cells is seen
What is ACPA?
- Anti CCP Antibody
- ACPA more specific for RA than RF
- useful prognostic marker
- ACPA +ve patients tend to have more severe and erosive disorders
Which test would you order when concerned about vasculitis?
ANCA - anti neutrophil cytoplasmic antibodies
Case 3:
- 53 yr old man
- 3 week history of fever, fatigue, muscle pain, night swears and weight loss
- urine dip contained blood
- lung granuloma formation
- raised creatinine and urea
- ANCA showed a +ve c-ANCA pattern
vasculitis
What is vasculitis and what are the general symptoms?
autoimmune inflammation of the blood vessels
fever, headache, fatigue, weight loss, general aches and pains
