Setting the bar differently: how to navigate old and new sets of criteria for the classification of antiphospholipid syndrome

EULAR 2023 classification criteria for the antiphospholipid syndrome (APS) [2].This set of criteria arranged clinical and laboratory features into "domains" and applied a scoring system that yields higher scores in patients without any concomitant risk factors for vascular thrombosis and/or pregnancy morbidity other than antiphospholipid antibodies (aPL).Nowadays, all the existing cohorts of APS patients have been built according to the previous classification criteria originally delivered in 1999 ("Sapporo Criteria") [3], and subsequently updated in 2006 ("Sydney Criteria") with the inclusion of anti-β 2 glycoprotein I antibodies (anti-β 2 GPI) among laboratory criteria [4].As longstanding observers within the APS field, we acknowledge that the comparison between "new" and "old" criteria can raise a few issues that need guidance (Figure 1).First, the inclusion of new clinical domains, namely suspected microvascular involvement, cardiac valve thickening and thrombocytopenia, may lead to the speculation that several patients might have been missed when applying the 2006 criteria.However, the single presence of one of these criteria does not yield a score more or equal to 3; therefore, each new clinical criterion alone does not fulfill the requirements for 2023 classification (except for cardiac valve vegetation).