Rheumatology Flashcards
(24 cards)
What does positive rheumatoid factor indicate?
RhF is an autoantibody directed against Fc domain of IgG
It is used in the diagnosis of rheumatoid arthritis - sensitivity 70-80%, specificity 85%.
Also positive in multiple other conditions:
- Felty’s syndrome (100%)
- Sjogren’s syndrome (100%)
- Mixed connective tissue disease (50%)
- SLE (40%)
- Systemic sclerosis (30%)
- Infection (50%)
- Normal people (2-10%)
What does positive anti-CCP indicate?
Very specific for diagnosis of RA (94-98% specific)
Sensitivity about 80%
Also predicts more aggressive disease in RA (more erosions)
What does positive anti-dsDNA indicate?
Very specific for diagnosis of SLE (95%)
Sensitivity about 60%
Levels of which antibody correlate with disease severity in SLE?
Anti-dsDNA
Which auto-antibody is specific for drug induced lupus?
Anti-histone
What are the antibodies used to test for antiphospholipid syndrome?
- Anticardiolipin
- Anti-beta-2 glycoprotein
- Lupus anticoagulant testing - involves three steps
- > Demonstration of prolonged phospholipid dependent screening test of haemostasis (either prolonged dilute Russel viper venom time (dRVVT) or prolonged lupus aPTT)
- > Mixing patient plasma with normal plasma fails to correct prolonged screening tests (suggests presence of inhibitor)
- > Addition of excess phospholipid shortens or corrects the prolonged coagulation test (demonstrates phospholipid dependence)
What does positive anti-Ro (SSA) antibody indicate?
Positive in Sjogren’s syndrome (40-95%), SLE (32%), systemic sclerosis (21%), RA (15%)
Associated with neonatal lupus (+ complete heart block)
What does positive anti-La (SSB) antibody indicate
In combination with +ve anti-Ro, it is quite specific for Sjogren’s or SLE
Associated with neonatal lupus (+ complete heart block)
What does positive anti-Smith Ab indicate?
Most specific test for SLE (99%) but not very sensitive (<30%)
What is the most specific antibody test for SLE? What is the most sensitive?
Most specific - anti-Smith (99%)
Most sensitive - ANA (98-100%)
What does positive anti-ribosomal P antibody indicate?
Highly specific for SLE (98%) but not very sensitive (15%)
Associated with CNS lupus and lupus hepatitis
What does positive anti-Jo-1 antibody indicate?
Assoc with polymyositis and anti-synthetase syndrome
What does positive anti-Mi-2 antibody indicate?
Assoc with dermatomyositis
What does positive anti-Scl70 (anti-topoisomerase I) indicate?
Highly specific for systemic sclerosis (100%) and particularly the diffuse type
Increased risk of pulmonary fibrosis/ILD
What does positive anti-centromere Ab indicate?
Specific for limited systemic sclerosis, particularly CREST syndrome
More likely to develop pulmonary HTN
What does positive c-ANCA antibody indicate?
c-ANCA is directed against PR3
(remember C = 3)
Highly specific + sensitive for granulomatosis with polyangiitis in the right clinical context (Wegener’s)
What does positive p-ANCA antibody indicate?
p-ANCA is directed against MPO
Positive in a variety of conditions including: microscopic polyangiitis, Churg-strauss, ulcerative colitis, PAN, RPGN
What does positive anti-U1-RNP indicate?
This antibody is always positive in mixed connective tissue disease
However it is also positive sometimes in SLE (40%)
Thus not specific for MCTD
What antibodies are associated with a SPECKLED ANA?
Speckled ANA - fine or coarse speckles throughout the nucleus
Associated with the ENAs:
- U1-RNP [MCTD]
- Sm [SLE]
- La, Ro [SS, SLE]
- SCl-70 (topoisomerase) [DcSSc]
- RNA polymerase II and III [DcScc]
What does positive anti-RNA polymerase III indicate?
Highly specific (>99.5%) for systemic sclerosis Assoc with DcSSc and in particular rapidly progressive skin involvement and development of scleroderma renal crisis
What conditions are associated with a HOMOGENOUS ANA?
Drug induced lupus, SLE, Sjogren’s, JIA
10% of normal population
What antibody is associated with a PERIPHERAL RIM ANA?
Anti-dsDNA (SLE)
What antibody is associated with a CENTROMERE ANA distribution?
Anti-centromere antibody
Condition - limited scleroderma, esp associated with pulmonary HTN
What antibody is associated with a NUCLEOLAR ANA staining pattern?
RNA polymerase I
Th
Pm-Scl
Conditions: SLE, diffuse scleroderma, polymyositis, nucleolar dot with PBC, 5% normal population
