Rheumatology Screening Panels


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Rheumatology Screening Panels

  1. 1. Rheumatology Screening Panels A Utilization Intervention at St. Michael’s Hospital Created by Jeff Warshafsky Division of Rheumatology St. Michael’s Hospital
  2. 2. Rheumatoid Factor (RF): This test can be used alone or along with other diagnostic tests to identify specific autoimmune/rheumatologic or even infectious and malignant diseases. The test identifies the presence of a RF (an antibody {G,A,or M}) directed specifically against the CH2/3 domain of IgG. The titre may be relevant in some but not all conditions for disease monitoring (eg infections such as SBE or Tb), but a positive test is significant. ESR: This test can be ordered to measure the erythrocyte sedimentation rate to help diagnose a few diseases but is mainly used to monitor patients with other autoimmune/rheumatologic diseases that cause inflammation. CRP (C-reactive protein): Produced by the liver, CRP is an indicator of inflammation that may be associated with an autoimmune/rheumatologic or infectious disease. This test measures the levels of C-reactive protein in the patient’s blood. ANA: If the ANA is positive, the laboratory automatically performs Extractable Nuclear Antigens (ENA) and Double Stranded DNA Antibody (dsDNA) tests. If the ANA is negative, one may still request the Autoimmune Screen Panel II (Advanced) depending on the working diagnosis. Once the ANA has tested positive there is no diagnostic benefit in repeating this test. Please remember that an ANA may also be positive in up to 5% of normal young females and decisions to proceed with further testing should always take into account overall clinical and laboratory features. DO NOT REPEAT POSITIVE ANA TESTS!!! ENA: If the ANA is positive, the diagnostic laboratory will automatically perform an ENA screen for the following antibodies: Anti-SSA (Ro), Anti-SSB (La), Anti-Smith, Anti-SM-RNP, Anti-Scl-70 and Anti-Jo- 1. The presence of these antibodies in the patient can be useful diagnostically: e.g Sjogren’s syndrome, SLE and mixed connective tissue disease, or polymyositis. This test should not be ordered if an ANA is negative except under very specific circumstances which should be discussed with the rheumatology service. dsDNA: Once an ANA has come back positive, the diagnostic laboratory will also automatically perform a dsDNA screen by ELISA. A positive result supports the diagnosis of SLE and can be used to monitor disease activity in some patients. This test will not be ordered if the ANA is negative. Autoimmune Screen Panel I (Basic)
  3. 3. aPTT: This test is used to measure how well the patient’s blood is clotting. It may be prolonged in association with autoimmune/rheumatologic disease and coagulopathies. C3, C4, CH50: These tests measure the levels of complement proteins in a patient’s blood. The C4(classical pathway) and C3 (alternate) are static measures of the serum levels of these proteins, whereas the CH50 is a functional assay that correlates with the complement cascade activity. If the measured values are not within the reference range, this may be indicative of an autoimmune/rheumatologic disease with immune complex deposition. SPEP (Serum protein electrophoresis): This test is used to monitor albumin and globulin protein levels in a patient’s blood. If an autoimmune/rheumatologic disease is affecting these levels, the test results may be out of the reference range. Lower albumin levels may reflect chronic illness, elevated acute phase reactants infection or inflammation, elevated gammaglobulins inflammation and if a spike present, possible gammopathy. Coombs (direct): If an autoimmune/rheumatologic disease is suspected to be causing hemolytic anemia this test can check whether antibodies are indeed bound to red blood cells. This would indicate an autoimmune condition as the cause of the RBC destruction. Autoimmune Screen Panel II
  4. 4. Crystal Screen Panel Serum Uric Acid: This test is used to detect the level of uric acid in the patient’s blood. High levels of uric acid can lead to monosodium urate crystal build up in joints which causes gout. Ca, Phos, Mg: These tests measure the amount of these minerals in the patient’s blood. Several crystal arthropathies may be associated with abnormal levels of these minerals. Serum Iron, TIBC: These tests are ordered together to test for iron levels and saturation in the patient’s blood. Serum iron tests the amount of iron in the patient’s serum while TIBC tests how much iron the patient’s transferrin plasma proteins can bind. An elevated serum iron and increased saturation will be seen in Hemochromatosis, which can be a cause of CPPD arthopathy (pseudogout).
  5. 5. Vasculitis Screening Panel ANA, RF, ESR, CRP, SPEP: have been covered. ANCA (C/P): This test is used to diagnose necrotizing vasculitis. Patterns may vary e.g. in Wegener’s Granulomatosis (cytoplasmic – proteinase-3 or C pattern); or microscopic polyarteritis, Churg- Srauss, rapidly progressive glomerulonephritis (perinuclear – MPO, lactoferrin, elastase, cathepsin or P pattern). If present, anti- neutrophilic cytoplasmic antibodies (ANCA) are indicative of these diseases. In some cases the titre may be used to monitor disease activity and response to treatment, and can be reassessed periodically. Cryoglobulins: Cryoglobulins are immunoglobulins that reversibly precipitate in the cold. They are classified in 3 categories which correlate with their clonality (mono, poly, mixed). They may cause vascular injury (immune complex deposition) and are associated with a wide variety of clinical conditions including autoimmune rheumatic disease, infection and malignancy. Hep B s Ag: This tests for Hepatitis B surface antigen. This may be associated with Polyarteritis Nodosa. Anti-HCV: This test checks for antibodies to Hepatitis C Virus. A positive result indicates that the patient was at one time infected/exposed. This may be associated with vasculitis particularly those featuring cryoglobulinemia. Urine Routine: This test screens the patient’s urine for various substances. It can be ordered to screen for a wide variety of inflammatory diseases where red and white blood cells, casts and protein may be detected in urine. CK: This test measures the levels of creatine-kinase enzyme in the patient’s blood. Elevated levels indicate damage to the heart or other muscles that normally contain the enzyme. The lab will fractionate to define the origin (peripheral muscle, cardiac, brain).
  6. 6. aPTT/INR: These tests are used to measure how well the patient’s blood is clotting. If it is prolonged it may be indicative of an autoimmune/ rheumatologic disease and a mixing study will be performed to test for lupus anticoagulant (LAC). Haematology will determine if any other tests are necessary. Anti-cardiolipin: This test is used to identify anti-cardiolipin (anti- phospholipid) antibodies These may be present in a variety of autoimmune/rheumatologic diseases as well as other unique coagulopathies. DO NOT REPEAT +ve ANA TESTS!!! Autoimmune Coag Screen Panel I
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