Assessing Chronicity Index on Kidney Biopsies of Patients with Lupus Nephritis and Its Correlation with Creatinine and Proteinuria at 1-Year Follow-Up

Background: Lupus nephritis is a common manifestation of sistemic lupus erithematous and is associated with higher mortality, specially on those who progress to end-stage kidney disease. This study aims to assess chronicity index on initial kidney biopsy as a prognostic factor in lupus nephritis by correlating it to creatinine and proteinuria after 1-year follow-up. Methods: Patients diagnosed with lupus nephritis between January 2012 and December 2018 were included. Study variables comprised age, gender, creatinine, estimated glomerular filtration rate (eGFR) by CKD-EPI, proteinuria, histological class and chronicity index on renal biopsy. Results: A total of 253 renal biopsies were performed on the studied period, 86% in women. Mean age was 31 years old (13-70), initial serum creatinine 1.3 mg/dL (0.3-8.0) and final 1.47mg/dL (0.4-13.2). Average eGFR was 58 mL/min (4-156) at the time of kidney biopsy and 82mL/min (4-156) a year later, with average proteinuria going from 1.9g (0.1-10.7) on initial measure to 0.37g (0.04-6.9) after 1 year. Median chronicity index on kidney biopsy was 3 (0-10). Spearman correlation between chronicity index and creatinine after 1 year was 0.538 with p < 0.001, and with proteinuria was 0.144 with p 0.047. Chronicity index ≤ 4 was associated with lower proteinuria (p 0.02) and lower creatinine (p < 0.001) at 1 year of follow-up. Conclusion: Patients with high chronicity indices at diagnosis present worse renal function and higher levels of proteinuria during follow-up. Supportive care and degree of immunosuppression in the setting of chronic and irreversible histologic lesions are topics that need more attention in such scenarios.