Identifying phenotypes of patients with antiphospholipid antibodies: results from a cluster analysis in a large cohort of patients

Abstract

Abstract Objectives To identify the aggregation of patients with aPL into different subgroups sharing common features in terms of clinical and laboratory phenotypes. Methods We applied a hierarchical cluster analysis from the multiple correspondence analysis to determine subgroups of patients according to clinical and laboratory characteristics in a cohort of subjects with confirmed aPL positivity who presented to our outpatient clinics from 2006 to 2018. Results A total of 486 patients [403 women; age 41.7 years (26)] were included, resulting in five clusters. Cluster 1 (n= 150) presented with thrombotic events (65.3% with venous thrombosis), with triple aPL positivity found in 34.7% of them (the highest rate among the different clusters). All the patients from cluster 2 (n = 91) had a confirmed diagnosis of SLE and the highest rate of anti-dsDNA positivity (91.7%). Cluster 3 included 79 women with pregnancy morbidity. Triple positivity was present in 3.8%, significantly lower when compared with Cluster 1 (34.7% versus 3.8%, P <0.01). Cluster 4 included 67 patients, 28 (41.8%) of whom with APS. Thrombotic events were observed in 23.9% patients. Cluster 4 had the highest rate of cytopenia, with thrombocytopenia as high 41.8% with no anti-dsDNA antibodies. Cluster 5 included 94 asymptomatic aPL carriers. Conclusion While clusters 1, 2, 3 and 5 corresponded to well-known entities, cluster 4 might represent a bridging condition between pure primary APS and defined SLE, with lower thrombotic risk when compared with primary APS but higher general features such as ANA and cytopenia (mainly thrombocytopenia).