Background The effect of antiphospholipid antibodies (aPL) on organ damage in Systemic Lupus Erythematosus (SLE) patients remains unclear as there is a limited number of studies with contrasting conclusions.
Objectives The aim of this study was to assess the relative contribution of aPL to organ damage in SLE patients.
Methods SLE patients (based on American College of Rheumatology [ACR] Classification Criteria) with less than 10 years of disease duration at registry entry were identified from the SLE registry of two centers. Clinical information retrieved included: demographics, disease duration, organ damage assessed by the Systemic Lupus International Collaborating Clinics/ACR Damage Index (SDI), and aPL profile. A “clinically significant” aPL profile was defined as: positive lupus anticoagulant test, anticardiolipin antibody IgG/M >40 GPL or MPL, and/or anti-β2Glycoprotein-I IgG/M > the 99th percentile), on two or more occasions, at least 12 weeks apart, within ±1 year of registry entry. The outcome variables were any increase of SDI at 5, 10 and/or 15 years of follow-up (time 0 was defined as registry entry). For univariate analysis the demographic and clinical characteristics of patients with and without a SDI increase at 5, 10 and 15 years were compared (Chi square or Fisher's exact test for categorical data, Student t test or Mann-Whitney-Wilcoxon for continuous data as appropriate). The Generalized Estimated Equations (GEE) model was used as multivariate analysis to detect significant factors for increased SDI at 5, 10 and/or 15 years.
Results We identified 262 patients with less than 10 years of disease duration, at least 5 years of prospective follow-up and a complete aPL profile (76% Caucasian, 8% African-American, 6% Asian, and 86% female). Mean age at diagnosis was 31 years (±12) and mean age at registry entry was 33 years (±12) with a mean disease duration of 1 year (±2). Eighty-eight (33%) patients had a clinically significant aPL profile. Twenty-one percent, 42%, and 57% of patients had new organ damage in 5, 10, and 15 years, respectively (Table I). On the univariate analysis: a) a significant aPL profile (p:0.02) and a older age at diagnosis (p:0.04) were significantly associated to any increase of SDI at 5 years; b) a shorter disease duration was significantly associated to any increase of SDI at 10 years (p:0.003) and 15 years (p:0.008); and c) male gender showed a tendency for any increase of SDI at 15 years without reaching significance (p:0.054). The GEE model showed that patients with a significant aPL profile (p:0.006,Odds Ratio, [OR]:1.9, 95% Confidence Interval,[CI]:1.2-3.1), older age at diagnosis (p:0.007, OR: 1.02, 95%CI 0.006-0.04) or male sex (p:0.017,OR: 1.9,95%CI 1.1-3.3) were more likely to experience an increase of SDI during the follow-up (Table II).
Conclusions Our data demonstrate that: a) one-third of SLE patients have clinically significant aPL profiles; b) 21%, 42% and 57% of SLE patients have new organ damage in 5, 10 and 15 years; c) clinically significant aPL-profiles, older age at diagnosis, and male sex are associated with an increased risk of organ damage accrual during a fifteen year follow-up.
Disclosure of Interest None declared