Systemic lupus erythematosus in three ethnic groups. XII. Risk factors for lupus nephritis after diagnosis

Abstract

The purpose of this study was to determine the cumulative incidence of lupus nephritis (LN) and the factors predictive of its occurrencein a multiethnic systemic lupus erythematosus (SLE) cohort. We studied 353 SLE patients as de” ned by the American College of Rheumatology (ACR) criteria (65 Hispanics, 93 African-Americans and 91 Caucasians). First, we determined the cumulative incidence of LN in all patients. Next, we determined the predictors for LN in those with nephritis occurring after diagnosis. The dependent variable, LN, was de” ned by: (1) A renal biopsy demonstrating World Health Organization (WHO), class II–V histopathology; and/or (2) proteinuria≥ 0.5 g=24 h or 3 + proteinuria attributable to SLE; and/or (3) one of the following features also attributable to SLE and present on two or more visits, which were performed at least 6 months apart— proteinuria≥ 2 +, serum creatinine≥ 1.4 mg/dl, creatinine clearance ≤ 79 ml/min, 10 RBCs or WBCs per high power ” eld (hpf), oŗ 3 granular or cellular casts per hpf. Independent variables assessed at diagnosis, and if absent, at baseline, were from four domains: sociodemographic, clinical, immunologic and immunogenetic (including the complete antibody pro” le and MHC class II alleles), and health habits. Variables with P < 0.05 by chi square analyses were entered into domain-speci”c stepwise logistic regression analyses controlling for disease duration, with LN as the dependent variable. Signi” cant domain-speci”c regression variables (P ≤ 0.1) were then entered into an overall model. The cumulative incidence of LN was 54.3% in all patients, and 35.3% for those developing LN after diagnosis. LN after diagnosis occurred in 43.1% of 65 Hispanics, 50.5% of 93 African-Americans, and 14.3% of 91 Caucasians, P < 0.0001. The duration of follow-up for those with LN after diagnosis was 5.5§ 2.4 vs 4.0§ 2.9 years for those without LN. Hispanic (odds ratio (OR) = 2.71, 95% con” dence limits (CL) = 1.07–6.87, P < 0.04) and African-American ethnicities (OR = 3.13, 95% CL = 1.21–8.09, P < 0.02), not married or living together (OR = 3.45, 95% CL = 1.69–7.69, P < 0.0003), higher SLAM score (OR = 1.11, 95% CL = 1.02–1.19, P < 0.007), anti-dsDNA (OR = 3.14, 95% CL = 1.50–6.57, P < 0.0001) and anti-RNP (OR = 4.24, CL = 1.98–9.07, P < 0.0001) antibodies were shown to be signi” cant predictors of the occurrence of LN. Repeated analyses excluding the patients with missing HLA data showed that absence of HLA-DQB1*0201 was also a signi” cant predictor for the occurrence of LN (OR = 2.34, CL = 1.13–5.26, P < 0.04). In conclusion, LN occurred signi” cantly more often in Hispanics and African-Americans with SLE. Sociodemographic,clinical and immunologic/immunogenetic factors seem to be predictive of LN occurring after the diagnosis of SLE has been made.