Some markers can be positive even in those who do not suffer from autoimmune diseases and should be evaluated only in the presence of clinical suspicion
A few years ago, while being tested for a suspected arthritis, I underwent tests for autoantibodies such as rheumatoid factor, anti-citrulline, anti-nuclear, anti-ENA, ANCA, negative results. How often should I repeat these tests (or possibly others) to rule out the presence of a rheumatological or other disease?
He answers Charles SelmiHead of Rheumatology and Clinical Immunology, Humanitas Institute, Milan (VAI AL FORUM)
Immunoglobulins (antibodies) directed against parts of our own body are defined autoantibodies and are configured as important signs of autoimmunity, a phenomenon that is observed in many rheumatological diseases (such as rheumatoid arthritis or connect them as systemic lupus erythematosus), and other types (such as autoimmune thyroiditis or type 1 diabetes). Many of these markers often have high sensitivity (i.e. they are positive in most people who have a certain autoimmune disease), but low specificity (i.e. they are they can be positive even in those who do not suffer from an autoimmune disease) and for this reason they must be requested only if there is a clear clinical suspicion, therefore linked to the symptoms. in fact it is very important that the result is interpreted on the basis of the reason why the prescription occurred. For example, in case of repeated miscarriages or venous or arterial thrombotic phenomena, they are sought antiphospholipid autoantibodies (LAC, anti-cardiolipin and anti-beta2 glycoprotein I) which on the contrary, if found without clinical manifestations, have a very uncertain significance.
Two cases deserve a more in-depth discussion, as the definition of autoantibodies allows for greater personalization of clinical management. The first concerns rheumatoid arthritiswhich manifests the negativity of rheumatoid factor or anti-citrulline antibodies in about 20% of the cases in which it is defined as seronegative. The seronegative form of rheumatoid arthritis has generally less aggressive clinical features than the seropositive formas the positivity of antibodies, especially anti-citrulline (ACPA), is associated with a greater risk of bone damage with erosions and therefore with the need for a different pharmacological treatment. The second example concerns instead a rare form of connective tissue disease called dermatomyositisin which a few dozen rare autoantibodies are known, some of which can only be determined in research laboratories.
These autoantibodies allow early identification of some important features of dermatomyositis such as pulmonary involvement or the presence of as yet undiagnosed malignancies. In general, with few exceptions, if there are no clinical reasons to think that the picture may have changed or that a previous test is technically unreliable, there is no reason to re-test autoantibodies after a negative result. This is especially true for the most common autoantibodies, ie the ANAs, which are positive in over 30% of people after the age of 50 and whose positivity and related title do not change over time. Similarly, autoantibody titers do not generally correlate with disease activity; an exception are autoantibodies against native DNA (dsDNA), which are very specific for systemic lupus erythematosusin which they correlate with the presence and severity of renal manifestations and are therefore re-checked over time to evaluate the effectiveness of the treatment.
February 12, 2023 (change February 12, 2023 | 09:42)
© breaking latest news