To investigate factors predictive of future lupus nephritis development when systemic lupus erythematosus (SLE) is diagnosed.
Patients with newly diagnosed SLE without renal manifestations were followed for development of lupus nephritis, comparing findings at baseline between those who did or did not develop nephritis. Albumin-to-globulin ratio (AGR) was calculated as albumin/(total protein-albumin). Cox proportional hazard model was used to identify predictors of lupus nephritis.
Of 278 patients, 241 did not and 37 did develop lupus nephritis during follow-up. On univariate analysis, young age, low C3, low C4, high anti-dsDNA titre, anti-Sm antibody, anti-RNP antibody and low AGR were associated with a higher risk of lupus nephritis. On multivariate analysis, factors predictive of nephritis were age [adjusted hazard ratio (aHR) 0.928, 95% confidence interval (CI): 0.895-0.961, p < 0.001], C3 (aHR 0.977, 95% CI: 0.966-0.989, p < 0.001), anti-dsDNA titre (aHR 1.004, 95% CI: 1.000-1.007, p = 0.026) and anti-Sm antibody (aHR 2.097, 95% CI: 1.040-4.229, p = 0.038). In particular, a low AGR (aHR 4.972, 95% CI: 2.394-10.326, p < 0.001) was strongly associated with an increased risk of future lupus nephritis development.
Young age, low C3, high anti-dsDNA titre and presence of anti-Sm antibody at diagnosis of SLE were associated with a risk of future lupus nephritis, but the hazard was greatest with a low AGR value, suggesting that a greater proportion of immunoglobulin relative to total protein is associated with the development of nephritis.