Diagnostic Testing in Rheumatology Lecture Powerpoint Flashcards
Rheumatoid factor
An antibody directed against the Fc portion of IgG found in 80% of RA patients, correlates with being a more severe disease and having extra-articular disease with seronegative RA having better prognosis, titers do not change or correlate with disease activity
What other conditions can rheumatoid factor be found in? (5)
- bacterial infection
- viral infeection
- sarcoidosis
- SLE
- pulmonary fibrosis
Anti-citrullinated peptide antibody CCP antibody test
Antibody that may be present prior to appearance of RA symptoms, may be as sensitive as rheumatoid factor for diagnosing RA but much more specific**, rarely present in arthropathies associated with hep C
Antinuclear antibody test
Positive in 99% of patients with SLE, negative ANA rules out diagnosis of SLE, but can also be found in other connective tissue diseases or drug induced so not diagnostic*** not useful to monitor disease activity
Anti DNA antibody test
Very specific for lupus with very few false positive results, but not very sensitive depending on disease progression
Anti SSA/SSB antibodies test
Associated 70% with sjogren’s syndrome and ANA negative lupus (rare), if seen in pregnancy can indicate neonatal lupus syndrome and congenital heart block
Anticardiolipin antibody test
Seen in recurrent venous or arterial thrombosis (in young unexpected cases with antiphospholipid antibody syndrome) or recurrent fetal loss
Antineutrophil cytoplasmic antibody (ANCA) test (c-ANCA, p-ANCA)
Found in patients with vasculitis associated with wegener’s granulomatosus and some rapidly progressing glomerulonephritis
Sed rate
Nonspecific test for inflammation, useful in diagnosis and monitoring of polymyalgia rheumatica and giant cell arteritis, sometimes useful in diagnosis and monitoring RA, vasculitis, SLE, etc
Lyme testing
Should only be done in suspected clinical setting, not useful for screening
Synovial fluid analysis
Can be analyzed for gross exam, leukocyte count, wet prep, gram stain, and cultures
Synovial fluid group 1
Present in noninflammatory conditions such as osteoarthrtiis, trauma, is pale yellow, transluscent, high viscosity
Synovial fluid group II
Present in inflammatory conditions such as RA, spondyloarthropathies, and microcrystalline disease, deeper yellow color and opaque
Synovial fluid group III
Present in septic fluid, purulent and opaque with WBC often very high, opaque, associated with positive gram stains and cultures
Synovial fluid group IV
Present in hemorrhagic fluid, has bloody appearance, due to trauma, bleeding disorders, tumors, etc.
