Autoantibodies

Question 1

ANA

Answer 1

SLE screening test (95% sensitive, poor specificity)

Question 2

Anti-double stranded DNA

Answer 2

SLE (60% sensitive). Correlates with lupus disease activity. More specific for kidney involvement.

Question 3

Anti-smith

Answer 3

SLE. Most specific test.

Question 4

Anti-U1-RNP

Answer 4

MCTD (High titers seen 1:10,000)
SLE
100% sensitive

Question 5

Anti-Ro/SSA

Answer 5

Sjogren syndrome (70% sensitivity)
SLE (30% sensitivity). Associated with neonatal lupus.
RA
Progressive systemic sclerosis (PSS)

Question 6

Anti-La/SSB

Answer 6

Sjogren syndrome (70% sensitivity)
SLE (30% sensitivity). Associated with neonatal lupus.
RA
Progressive systemic sclerosis

Question 7

Anticentromere

Answer 7

Limited PSS (CREST). Associated with pulmonary hypertension.

Question 8

Anti-Scl-70

Answer 8

Diffuse PSS. Associated with pulmonary fibrosis.

Question 9

c-ANCA (antiproteinase-3)

Answer 9

Granulomatosis w/polyangitis (Wegner). 90% sensitive when the disease is active.

Question 10

p-ANCA (antimyeloperoxidase)

Answer 10

Microscopic polyangitis (MPA)
Churg-Strauss syndrome (CSS)

Question 11

Anti-jo 1

Answer 11

Myositis. Associated with interstitial lung disease.

Question 12

Rheumatoid factor

Answer 12

Rheumatoid arthritis (70% sensitive, no specific for RA)
Sjogren syndrome
Cryoglobulinemia

RF is an antibody to Ig and therefore has many false positives. 30% of RA patients are RF negative.

Question 13

Anti-CCP

Answer 13

Rheumatoid arthritis (more specific for RA than RF)

Positive in up to ⅓ of RF negative RA patients. Associated with erosion. Predicts disease progression in patients with undifferentiated arthritis.

Question 14

Anti-histone

Answer 14

Drug induced SLE (95% sensitivity)

Question 15

Cryoglobulins

Answer 15

Vasculitis
Hepatitis C
SLE
RA