overview of rheumatology labs: alphabet soup? pediatric rheumatology red team resident teaching...

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  • Slide 1
  • Overview of Rheumatology Labs: Alphabet soup? Pediatric Rheumatology Red Team Resident Teaching Series
  • Slide 2
  • What are all those letters? ESR ANA CRP dsDNA ENA RNP Smith SS-a/SS-b Cardiolipin Jo-1 CPK p-ANCA/ c-ANCA RF C3/C4 CH50 Histone Centromere Scl-70 VDRL/RPR DRVVT Beta 2 glycoprotein 1 LDH Aldolase
  • Slide 3
  • Background Rheumatology spans a group of diseases that have auto-immune components Proposed mechanisms to auto-immunity including cross reactive antigens, molecular mimicry, and autoantibody amplification We can identify auto-antibodies and therefore characterize clinical diseases However, presence of auto-antibodies does not always predict disease
  • Slide 4
  • Diagnostic vs. Evaluative Tests Need to distinguish to determine which test is appropriate Diagnostic tests accurately distinguish a group of patients with a specific disease from a non-disease group Evaluative tests monitor disease activity over time
  • Slide 5
  • Erythrocyte Sedimentation Rate (ESR) Mainly used as a disease activity indicator Method: Westergren method (most common) which measures the rate of settling of RBCs in anticoagulated whole blood Nonspecific test of inflammation Elevated in infection, IBD, cancer, pregnancy, trauma, and stress Can be falsely low in conditions that dont let RBCs undergo rouleaux formation (sickle cell anemia, Hereditary Spherocytosis, CHF, polycythemia)
  • Slide 6
  • Anti-nuclear Antibodies (ANA) Immunoglobulins directed against structures within the cell (i.e. DNA, ribonuclear proteins, histones, and centromere) Titer is important; pattern not important Found in a variety of autoimmune diseases such as SLE, MCTD, JRA, scleroderma, Sjogrens syndrome in high titers (>1:320) Almost always present in SLE (95-98%) Low titers (
  • ANA Subtype: Double Stranded DNA (anti-dsDNA) Anti-dsDNA antibody is an ANA subtype In higher titers, highly specific for SLE Seen in >80% of SLE patients at some time during their course Associated with the presence of active lupus nephritis Can detect flare up before clinically significant Check anti-dsDNA levels if you suspect SLE in a child with positive ANA
  • Slide 8
  • ANA Subtype: Anti-Extractable Nuclear Antibodies (anti-ENA) anti-Smith (Sm) and anti-ribonucleoprotein (RNP) Both are directed against RNA proteins and are readily soluble in neutral buffers Anti-RNP is specific for MCTD (high titer) Anti-Sm ab is highly specific for SLE 10-20% in Caucasians, 30% in Asians, 40% in African Americans One of the lupus criteria
  • Slide 9
  • ANA Subtype: Anti Ro/SS-A and Anti La/SS-B Associated with Sjogrens, SLE, and neonatal lupus Anti Ro/SS-A antibodies seen in: 5-15% of normals 50% of Sjogrens patients 30% of SLE patients (many have negative ANA or subacute cutaneous lupus) Correlates with active nephritis and cytopenias Crosses the placenta and is associated with neonatal SLE and heart block Anti La/SS-B antibodies seen in: 5% of normals 15-85% of Sjogrens patients 10-15% of SLE patients Also associated with neonatal SLE but do not see the cardiac manifestations
  • Slide 10
  • ANA Subtype: Anticentromere, Anti- Scl-70, and Antihistone Antibodies Anticentromere Antibodies seen in limited cutaneous systemic sclerosis Anti-Scl-70 Antibodies (also known as anti-topoisomerase I) are assoicated with increased risk of pulmonary fibrosis in both limited and diffuse cutaneous systemic sclerosis Anti-histone antibodies are found in 95% of patients with drug-induced lupus syndrome Seen with: Procainamide Quinidine Hydralazine Phenytoin or other anti-epileptics
  • Slide 11
  • Antineutrophil Cytoplasmic Antibodies (ANCA) Associated with vasculitides Used as diagnostic test and possibly an evaluative test (still questionable) 2 main staining categories: c-ANCA and p-ANCA: Cytoplasmic ANCA (c-ANCA) coarse granular staining of the cytoplasm. The main antigen is proteinase-3 (PR3). Seen in 90% of Wegeners granulomatosis. Perinuclear ANCA (p-ANCA) staining of the nucleus and perinuclear area leaving cytoplasm clear. Main antigen is myloperoxidase (MPO). Associated with microscopic polyarteritis nodosa, Churg-Strauss, and Ulcerative Colitis.
  • Slide 12
  • Rheumatoid Factor (RF) Uncommon in children Should NOT be used as a screening test for rheumatic disease in children Only indication is for polyarticular JIA patients to classify and offer prognostic information Low titers seen in healthy children (