In recent years, a new class of autoantibodies associated with rheumatoid arthritis (RA) has been described and increasingly used as a diagnostic test.1-8 These antibodies, including anti–perinuclear factor and antifilaggrin antibodies target citrulline, a modified form of arginine produced through the action of peptidyl-arginine-deaminase. By consensus, these antibodies are now called anti–cyclic citrullinated peptide (anti-CCP) antibodies. For patients meeting classification criteria for RA, the anti-CCP antibody test (hereafter, anti-CCP test) has a reported sensitivity (frequency of positive results in the presence of disease) of 50% to 70% and specificity (frequency of negative results in the absence of disease) of 95% to 98%.1-7 Some of the variation in sensitivity and specificity across studies may be related to newer generations of the test measuring different antibody subtypes.7 A recent meta-analysis reported the sensitivity and specificity of the anti-CCP test for RA as 67% and 95%, respectively.8
Shmerling RH. Testing for Anti–Cyclic Citrullinated Peptide Antibodies: Is It Time to Set This Genie Free? Arch Intern Med. 2009;169(1):9–14. doi:10.1001/archinternmed.2008.522
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