#5081 THE VALUE OF ANTI-C1Q ANTIBODIES IN PREDICTING THE CLINICAL-HISTOLOGICAL FEATURES OF LUPUS NEPHRITIS PATIENTS AT TIME OF KIDNEY BIOPSY

Abstract

Abstract Background and Aims Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with renal involvement in around 50% of patients. Delayed diagnosis of lupus nephritis (LN) is associated with higher risk of end-stage kidney disease (ESKD) and mortality. Kidney biopsy remains the gold standard for diagnosis and management of LN, but in the last decades there is an interest for new serum biomarkers. Anti-C1q antibodies are autoantibodies associated with LN. Nevertheless, few studies have correlated the association of anti-C1q antibodies with active LN with focus on renal histology. Method We evaluated clinical and histological data of 59 patients with biopsy proven LN. Kidney biopsies were categorized following the ISN/RNP Classification. We evaluated the correlation of the main clinicopathologic features with values of antiC1q antibodies, measured by a commercial kit with a clinically validated ELISA test. Normal values of antiC1q were < 20 UA, medium values were between 20 and 80 UA and high values were > 80 UA. Demographic and clinical data were expressed as numbers or percentage for discrete variables and for continuous variables as mean and standard deviation. The correlation between antiC1q levels and clinicopathological characteristics have been analyzed with Fisher's test. Results At the presentation of 59 patients with LN, the mean age was 34 years and the time of SLE disease before the onset of LN was 73.2 months. 9 patients were male, mean serum creatinine was 1 mg/dl, glomerular filtration rate (eGFR) was 88.53 ml/min, proteinuria was 4.35 g/day and microscopic hematuria was present in 79% of pts. Kidney biopsies were classified as non-proliferative (class II and V) in 18.4% of patients and proliferative (class III and IV) in 77.6% of patients. We evaluated the correlation between all variables included in Table 1 with values of antiC1q antibodies and we found significant results for serum creatinine, active urinary sediment, C3 and C4 values, proliferative classes and the activity index at kidney biopsy (Table 2). Conclusion High titles of anti-C1q antibodies were significantly correlated with the main clinical and histological characteristics that identify active renal diseases in SLE. Kidney biopsy remains the gold standard for diagnosis and management of LN, but anti-c1q antibodies are strongly associated with active LN in SLE. In conclusion, anti-C1q monitoring should be helpful and might be a crucial serum biomarker for the diagnosis and follow-up of these patients.