Background Lupus nephritis (LN) is one of the most common and serious complications of Systemic Lupus Erythematosus (SLE). There are several factors that are considered related to the development of LN like malar erythema, anti-dsDNA and low serum complement. However not all patients with high level of anti-dsDNA or low level of serum complement present LN.
Objectives To determine if patients with low serum complement, high level of anti-dsDNA and malar erythema are more likely to have NL and analyze other clinical and immunological characteristics associated with NL.
Methods This is an observational, retrospective study in which 30 patients with LN, diagnosed with renal biopsy are compared with 61 SLE patients without LN, followed in the Rheumatology Unit of the University Hospital Ramόn y Cajal in the last 15 years. We excluded the patients diagnosed with other non lupus nephropathy or other associated autoimmune disease. The triad we've studied was the simultaneous presence of malar erythema, low level of serum complement (C3 and/or C4, <90 mg/dl and <10 mg/dl respectively) and high level of anti-dsDNA title (more than 3 times the normal limit as the standard technique >45 IU/ml by EliAUniCAP). Clinical and immunological data were collected following a review of medical records and analyzed using bivariate and multivariate methods in SPSS version 20.
Results Patients with NL were significantly younger at diagnosis of SLE than the control group (26.4±10.7 years vs 32.7±12.5 years), p=0.022. There were no differences between gender, ethnicity and time of evolution of SLE. In bivariate analysis, significant associations between NL and malar erythema (OR 6.25, p=0.0001), oral ulcers (OR 2.68, p=0.029), leukopenia (OR 2.97, p=0.034), lymphopenia (OR 5.5, p=0.001), serositis (OR 3.4, p=0.013) and fever (OR 2.56, p=0.045) were observed. Among the immunological parameters that are associated with NL were anti-dsDNA>45 U/ml antibody (Cramer's V =0.360, p=0.001), anti-U1RNP (OR 3.2, p=0.013), and low level of complement (OR 10.3, p=0.008). Chronic cutaneous lupus erythematosus and rheumatoid factor had a negative association with LN (p=0.02; p=0.049 respectively). The LN type IV was significantly associated with the studied triad (p=0.013). In the multivariate analysis the patients who had the triad were more likely to have LN (OR 42.5, 95% CI 7.7 to 233, p=0.0001); in 75% of these patients the time from the onset of the triad to the onset of LN was equal to or less than 10.2 months. The triad has higher specificity than anti-dsDNA alone (93.4% vs 55%), but lower sensitivity (76.6% vs 96%), the positive predictive value of the triad was 85% and the negative predictive value was 89%.
Conclusions The presence of the triad (malar erythema, low level serum complement and anti-DNAds) is an important predictive factor for the development of lupus nephritis and more specific than the presence of each of these alterations separately. Given these results, although larger studies are needed to confirm this profile, special care must be taken to the patients with this clinical and analytically features.
Ravirajan CT, et al. An analysis of clinical disease activity and nephritis-associated serum autoantibody profiles in patients with systemic lupus erythematosus: a cross-sectional study. Rheumatology (Oxford) 2001;40:1405–12.
Disclosure of Interest None declared