AB0318 RISK FOR CONCOMITANT AUTOIMMUNITY IN PATIENTS WITH ANTIPHOSPHOLIPID SYNDROME; A SWEDISH COHORT STUDY

Abstract

Background:In patients with the antiphospholipid syndrome (APS), concomitant systemic autoimmune rheumatic diseases (SARD) are common and often associated with more disease associated damage.Less is known about the prevalence of non-rheumatic autoimmune diseases (NRAID) in patients with APS.Objectives:To evaluate the incidence and prevalence of concomitant autoimmune diseases (AID) in a cohort of APS patients. The risk of AID was also evaluated with respect to the antiphospholipid antibodies (aPL) profiles.Methods:This retrospective cohort study comprises consecutive patients identified with APS through review of electronic medical records at Karolinska University Hospital, Sweden between 2014 and 2020. Exclusion criteria were misdiagnosis and age <18. Descriptive statistics was used for baseline data and multivariable Cox proportional hazard regression analysis to investigate the risk factors to develop new onset AID. Ethical approval was obtained from the Swedish Ethical Review Authority (2020-02333).Results:Of 271 included patients, 66% were women and the median age at diagnosis of APS was 43 years (IQR 31–55). At inclusion, 130 (48%) patients presented with other AID; 101 (37%) of them had a concomitant SARD while 54 (19%) had a NRAID. Systemic lupus erythematosus (SLE) was the most frequent in 30% of patients, followed by autoimmune thyroid disease (ATD) in 10% of patients.In addition, 35 (13%) APS-patients developed AID during the study period, corresponding to an incidence rate of 28.4 (95% CI; 19.3-40.3) per 1.000 person-years with mean time at risk of 4 (±2) years. Twenty-one (8%) patients developed a SARD and further 14 (5%) were diagnosed with a NRAID.The cumulative incidence for AID was significantly higher in patients with high titers of IgG aPL. Patients that developed SARD had significantly higher median titers of a-β2GPI IgG isotype, p=0.05. In the NRAID group, median a-β2GPI and aCL IgG isotypes were significantly increased, p=0.02 and p=0.04, respectively. The hazard ratio to develop diagnosis of AID was significantly increased in patients with high titers of the IgG isotype aPL (HR 2.4 95% CI; 1.1-5.3). Obstetric APS manifestations were associated with a significantly increased hazard ratio of 2.8 (95% CI; 1.1-7.7) to develop SARD, and also trendwise for AID, as a compound variable.During the study period, 52 patients had at least one new APS manifestation, as defined by the Sydney criteria (1). In comparison to patients without new manifestations, these patients had significantly higher median titers of aPL of the IgG isotype, and concomitant AID at first visit (p=0.01, p=0.02, respectively).Conclusion:APS patients are at high risk to develop other AID, and APS patients with concomitant AID had an increased risk to develop new clinical APS manifestations. These findings might be helpful when considering risk stratification and alternate treatment options in this patient group.