Anti-microtubule organizing center with microtubule by autoimmune target test is also useful serological marker in rheumatoid arthritis evaluation

Seropositivity of rheumatoid factor (RF) or anti-cyclic citrullinated peptide antibody (anti-CCP) is one domain of scoring system in new American College of Rheumatology/European League against Rheumatism classification criteria for rheumatoid arthritis (RA). We investigated usefulness of antiperinuclear factor (APF) and autoantibody to microtubule organizing center with microtubule (anti-MTOC-MT), which was detected by autoimmune target (AIT) test, as serological markers for the diagnosis of early RA. The test results of 3,503 patients from the outpatient clinic of The Hospital for Rheumatic Diseases who underwent test for RF, APF, anti-CCP and anti-MTOC-MT simultaneously for the work-up of RA were analyzed. Four kinds of tests showed same results only in 53.1% (1,861/3,503) of all subjects. The kappa coefficient between each test was distributed from −0.011 to 0.622. The agreement was best between RF and anti-CCP (kappa coefficient: 0.622), but the agreement was poor between anti-MTOC-MT and other 3 tests (kappa coefficient: 0.007 to −0.025). In both of RF- and anti-CCP-negative patients, the patients who showed positive result for APF were 4.6% (160/3,503) and for anti-MTOC-MT were 13.2% (464/3,503). RF and anti-CCP positivity could not include all of APF and anti-MTOC-MT positivity. Anti-MTOC-MT detected by AIT test was independent serological marker, and it might be also helpful for the diagnosis of early RA. Therefore, the combined detection of all four serologic markers can be useful for the evaluation of suspected RA patients.