Rheumatology Labs

ESR

a non-specific blood test that measures how quickly red blood cells settle at the bottom of a vertical test tube over one hour

-a high value indicates inflammation, infection, malignancy, or autoimmune activity but does not pinpoint the exact cause

-associated with Polymyalgia rheumatica, giant cell arteritis, RA, SLE, ankylosing spondylitis, and vasculitides

CRP

a non-specific test that measures an acute-phase reactant, which is a protein made by the liver in response to inflammation, infection, or tissue injury

-higher values generally indicate more intense inflammation

-associated with RA, ankylosing spondylitis, psoriatic arthritis, crystal arthropathies, and vasculitides

Rheumatoid Factor (RF)

IgM autoantibody against the Fc portion of IgG

-Associated with rheumatoid arthritis

Anti-cyclic citrullinated peptide (anti-CCP)

Autoantibody against citrullinated peptides/proteins

-Most specific test for rheumatoid arthritis

Antinuclear antibody (ANA)

Autoantibody to nuclear components, great screening test

-Associated with SLE, the most sensitive

Anti-double-stranded DNA (anti-dsDNA)

Autoantibody to native DNA, linked to immune complex deposition

-Associated with SLE, most specific test

Anti-histone antibodies

Autoantibody against histone proteins in chromatin

-Associated with drug-induced lupus, most specific

Anti-Smith (anti-Sm)

Autoantibody to small nuclear ribonucleoproteins

-Associated with SLE, most specific but less sensitive

Anti-small nuclear ribonucleoprotein (anti-snRNP)

Autoantibody to U1 snRNP involved in mRNA splicing

-Associated with mixed connective tissue disorder (MCTD), most specific

Anti-SSA (Rho)

Autoantibody to ribonucleoprotein, can cross the placenta

-Associated with Sjogren’s Syndrome

Anti-SSB (La)

Autoantibody to RNA-binding protein

-Associated with Sjogren’s Syndrome, not as specific as anti-SSA

Anti-topoisomerase I (anti-Scl-70)

Autoantibody to DNA topoisomerase I

-Associated with diffuse systemic sclerosis, most specific

Anti-centromere antibodies

Autoantibody to centromere proteins

-Associated with limited systemic sclerosis, most specific

Antineutrophil cytoplasmic antibodies (ANCA)

Autoantibodies to neutrophil cytoplasmic enzymes

-Associated with granulomatosis with polyangiitis, most specific

HLA-B27

Class I MHC allele linked to seronegative spondyloarthropathies

-Associated with ankylosing spondylitis, strongest genetic association

Anti-cardiolipin antibodies

Antiphospholipid antibodies against mitochondrial phospholipid

-Associated with antiphospholipid syndrome, one of the classification criteria

Lupus Anticoagulant

Antiphospholipid antibody that prolongs phospholipid-dependent coag tests

-Associated with antiphospholipid syndrome, one of the classification criteria