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In the 2010 RA classification criteria, developed by the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR), positivity for RF and/or ACPA yields two points for low-positive results (>1× ULN and <=3× ULN) or three points for high-positive results (>3× ULN) out of 10 points, with >=6 points indicative of definite RA [[6]]. Keywords: diagnostic performance; rheumatoid arthritis (RA); rheumatoid factor (RF) EN diagnostic performance rheumatoid arthritis (RA) rheumatoid factor (RF) e142 e145 4 05/12/22 20220501 NES 220501 To the Editor, Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic joint inflammation causing irreversible damage. Nevertheless, our data show that 24.7% of the RA patients (n=18/73 at manufacturer's cutoff) is negative for both tests, emphasizing that even a negative result for both RF and CCP3 is not sufficient to exclude RA. [Extracted from the article]

Background: Antibodies directed against dsDNA are a highly specific diagnostic marker for the presence of systemic lupus erythematosus and of particular importance in its diagnosis. To assess anti-dsDNA antibodies, the Crithidia luciliae-based indirect immunofluorescence test (CLIFT) is one of the assays considered to be the best choice. To overcome the drawback of subjective result interpretation that inheres indirect immunofluorescence assays in general, automated systems have been introduced into the market during the last years. Among these systems is the EUROPattern Suite, an advanced automated fluorescence microscope equipped with different software packages, capable of automated pattern interpretation and result suggestion for ANA, ANCA and CLIFT analysis. Methods: We analyzed the performance of the EUROPattern Suite with its automated fluorescence interpretation for CLIFT in a routine setting, reflecting the everyday life of a diagnostic laboratory. Three hundred and twelve consecutive samples were collected, sent to the Central Diagnostic Laboratory of the Maastricht University Medical Centre with a request for anti-dsDNA analysis over a period of 7 months. Results: Agreement between EUROPattern assay analysis and the visual read was 93.3%. Sensitivity and specificity were 94.1% and 93.2%, respectively. The EUROPattern Suite performed reliably and greatly supported result interpretation. Conclusions: Automated image acquisition is readily performed and automated image classification gives a reliable recommendation for assay evaluation to the operator. The EUROPattern Suite optimizes workflow and contributes to standardization between different operators or laboratories. [ABSTRACT FROM AUTHOR]