Background Elevated levels of antiphospholipid antibodies (aPL Abs) have been reported in over 30% of lupus (SLE) patients, and are associated with an increased risk of thrombosis. However, not all aPL Abs are pathogenic, and some may reflect chronic endothelial damage seen in chronic diseases, including cardiovascular disease and end stage renal disease (ESRD). Indeed, some studies reported the prevalence of aPL Abs as high as 30% in ESRD patients. The significance of these antibodies in ESRD remains controversial, but may be associated with an increased risk of thrombotic complications and cardiovascular mortality in these patients. Surprisingly, no studies to date ascertain the frequency of aPL Abs in SLE patients with ESRD.
Objectives To compare the frequency of elevated aPL Ab levels in SLE and non-SLE patients with ESRD from a large urban tertiary care center. We hypothesized that SLE patients will have a higher prevalence and a different pattern of aPL Abs compared with non-SLE ESRD patients.
Methods We identified all patients with ESRD at our center who had aPL Abs measured between 2005 and 2012. SLE was defined using ICD9 (International Classification of Disease) code (710.0). We also determined the prevalence of aPL Abs in a subgroup of patients who fulfilled the American College of Rheumatology criteria for SLE and had a history of biopsy proven lupus nephritis. IgA, IgG, and IgM isotypes were measured for the following aPL Abs: anticardiolipin (aCL), anti-beta2 glycoprotein I (anti-B2GPI), and antiphosphatidylserine (aPS). Positivity was defined as ≥20IU (“laboratory criteria”), and ≥40IU (“clinical criteria”). We used Fisher exact test to compare the frequencies of aPL Abs between non-SLE, SLE by ICD9 and SLE by ACR criteria vs. non-SLE.
Results We identified 116 non-SLE ESRD with aPL Abs measured, and 61 SLE ESRD with aPL Abs. Of the 61 SLE patients, 21 met ACR criteria for SLE and had biopsy proven lupus nephritis. The frequencies of aPl Abs are presented in Table 1. The prevalence of medium/high aPL Abs >40 IU was under 10% in both SLE and non-SLE ESRD. However, the prevalence and aPL Ab patterns were different among SLE and non-SLE patients.
Conclusions This is the first study to compare the prevalence of 3 aPL Ab types in SLE and non-SLE ESRD. Our data suggest that the overall prevalence of aPL Abs is higher in SLE than in non-SLE ESRD. The implications for thrombotic complications in SLE ESRD compared to non-SLE ESRD deserve further investigation.
Disclosure of Interest None declared