Background The performances of the anti-CCP have been evaluated in well defined cohorts of patients and controls but their relevance in rheumatological daily practice is less known in case of positivity of the results in patients not fulfilling the diagnostic criteria for rheumatoid arthritis (RA).
Objectives To evaluate the performances (sensitivity (Se), specificity (Sp) but also positive and negative predictive values (PPV, NPV)) of anti-CCP test and to check the diagnosis of the underlying disease of patients with positive anti-CCP and not fulfilling the diagnosis of RA.
Methods Study design: retrospective systematic evaluation of the diagnosis of patients who have been investigated for anti-CCP test (second generation) between December 2009 and December 2011.
Data collected: anti-CCP results in the department of immuno-biology of Cochin Hospital and diagnosis of the evaluated patients (according to medical file record).
Results Of the 634 evaluated samples, 74 were double (at least 2 evaluations in a same patient), no medical file was available for 28 samples and a diagnosis was not made in 15 patients, resulting in 517 evaluable patients. Anti-CCP was positive in 153 of the 222 RA patients, resulting in a sensitivity of 68,9%. Anti-CCP was negative in 282 of the 295 other patients, resulting in a specificity of 95,6%. PPV and NPV were respectively 92,2% and 80,3%. The 13 non-RA patients with positive anti-CCP were suffered from either undifferentiated monoarthritis (2 cases), Sjögren’s syndrome (2 cases), osteoarthritis, systemic lupus erythematosus with Sjögren’s syndrome (2 cases), juvenile idiopathic arthritis, mixed connective tissue disease, psoriatic arthritis (2 cases) or SAPHO. These 13 patients had a value of anti-CCP between one and three times the upper limit of normal (ULN) in 2 cases and over three times ULN in 11 cases.
Conclusions These data confirm the high sensitivity of anti-CCP in rheumatological setting, more importantly confirm also its high specificity and suggests than despite the high performances of this test, false positive and false negative results can be observed in daily practice. Non-RA anti-CCP positive patients can have anti-CCP values over ten times ULN.
Disclosure of Interest None Declared
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