AB0624 A Positive Rheumatoid Factor with Chronic Arthritis Protects Against Renal Involvement in Patients with Systemic Lupus Erythematosus
Authors: W. Louthrenoo, M. Areerug, N. Kasitanon, S. Wangkaew, W. Sukitawut, S. Puntana
Journal: Annals of the Rheumatic Diseases (2015)

<h3>Background</h3> Previous observation has found that SLE patients with arthritis tended to have less renal involvement, and the presence of rheumatoid factor (RF) might protect against lupus nephritis (LN). <h3>Objectives</h3> This study was performed to determine whether the presence of chronic arthritis (CA) protects against renal involvement or has less degree of nephritis in SLE patients. <h3>Methods</h3> The medical records of SLE patients, who were followed-up at the Division of Rheumatology, Chiang Mai University, were reviewed. Patients with CA were classified as a "case". Controls comprised SLE patients who were close to the case in hospital number, but had no chronic arthritis (NCA). The ratio of case to control was 1:2. SLE disease activity was determined by the modified SLE disease activity index-2000 (mSLEDAI-2K). The severity of SLE was ascertained by the sum of the Mexican SLEDAI score. Organ damage was detected by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR). Renal activity was determined by the SLICC Renal Activity/Response Exercise (SLICC/RARE). <h3>Results</h3> There were 46 cases (45 females) and 92 controls (90 females) with a mean age of 44.35±14.09 years and 42.03±13.61 years, respectively, and mean disease duration of 9.44±7.47 years and 9.75±7.17 years, respectively. Twenty-eight patients in the CA group had chronic arthritis before SLE diagnosis was made with a mean duration of 2.06±2.34 years (median 1 year). There was no significant difference between the CA and NCA group in the mSLEDAI score (3.50±5.15 vs. 3.25±4.73), the cumulative MEX-SLEDAI score (9.52±5.55 vs. 11.24±5.14), and the SLICC/ACR score (1.15±1.15 vs. 0.90±1.24); but the number of ACR classification criteria was significantly higher in the CA group (5.46±1.52 vs. 4.78±1.11, p=0.009). The CA group, within the ACR classification criteria, had significantly more arthritis (100% vs. 47.82%, p&lt;0.001), but less renal involvement (28.26% vs. 52.17%, p=0.008). There was no significant difference between the CA and NCA group in the prevalence of ANA (97.82% vs. 95.65%), anti-dsDNA (63.04% vs. 54.34%), anti-Sm (21.62% vs. 40.00%), anti-RNP (39.47% vs. 40.00%), anti-Ro (57.14% vs. 53.33%), anti-La (11.76% vs. 13.33%), and anti-cardiolipin antibodies (9.37% vs. 5.26%). Eleven patients (23.91%) in the CA group had positive RF (RF+). The time from the diagnosis of SLE to the onset of first LN was significantly longer in the CA group (10.24±7.43 months vs. 5.00±5.90 months, p=0.008). However, there was no significant difference between the CA and NCA group in the SLICC/RARE score (10.23±4.26 vs. 9.72±3.55), the maximum degree of 24-hour proteinuria (3.64±1.73 gm vs. 4.48±2.95 gm), and the maximum serum creatinine (1.50±1.05 mg/dL vs. 1.47±1.06 mg/dL) at first LN episode. Among the CA group, none of 11 cases with RF+ (0%), but 13 of 35 cases of those with RF- (37.14%) had renal involvement (p=0.02). <h3>Conclusions</h3> Significantly fewer SLE patients with CA had renal involvement than those with NCA, but there was no difference in the renal activity between the two groups. CA with RF+ is a protective factor for renal involvement in SLE patients. <h3>Disclosure of Interest</h3> None declared