TY - CHAP M1 - Book, Section TI - Diseases & Pathophysiology in Rheumatology A1 - Huppert, Laura A. A1 - Dyster, Timothy G. Y1 - 2021 N1 - T2 - Huppert’s Notes: Pathophysiology and Clinical Pearls for Internal Medicine AB - Rheumatologic conditions associated with a +ANA:Systemic lupus erythematosus (SLE)Systemic sclerosis (SSc)Myositis (often ANA-negative; ~50% of dermatomyositis/polymyositis cases are ANA-positive)Mixed connective tissue disease (MCTD)Primary Sjögren’sANA Testing Pearls:- Antinuclear antibodies (ANA) are autoantibodies that bind to the contents of the cell nucleus. The ANA test detects the ANA autoantibodies that are present in the patient’s serum.- ANA can be elevated in many disorders including autoimmune conditions, infection, and malignancy. 20% of healthy women have a positive ANA. Therefore, it is non-specific and should only be sent if clinical suspicion is high for one of the disorders above.- The level of autoantibody is reported as a titer, which is the highest dilution of the serum at which the autoantibodies are still detectable (e.g., 1:640 is more dilute than 1:80, suggesting more autoantibodies are present in the 1:640 sample). The probability of autoimmunity increases with higher ANA titers:ANA ≥1:80 required by EULAR/ACR SLE classification criteriaANA ≥1:640 → 95.8% specific for SLE- If an ELISA-based ANA test is negative but clinical suspicion for CTD high, ask the lab to carry out an immunofluorescence (IF)-microscopy-based ANA test, which is more specific. SN - PB - McGraw Hill CY - New York, NY Y2 - 2024/11/11 UR - accessmedicine.mhmedical.com/content.aspx?aid=1189914044 ER -