Validation of the Oxford Classification of IgA Nephropathy: A Single-Center Study in Korean Adults

Background/Aims: The recently published Oxford classification of IgA nephropathy (IgAN) proposed a split system for histological grading, based on prognostic pathological features. This new classification system must be validated in a variety of cohorts. We investigated whether these pathological features were applicable to an adult Korean population. Methods: In total, 69 adult Korean patients with IgAN were analyzed using the Oxford classification system at Soonchunhyang University Hospital, Seoul, Korea. All cases were categorized according to Lee's classification. Renal biopsies from all patients were scored by a pathologist who was blinded to the clinical data for pathological variables. Inclusion criteria were age greater than 18 years and at least 36 months of follow-up. We excluded cases with secondary IgAN, diabetic nephropathy combined other glomerulopathies, less than 36 months of follow-up, and those that progressed rapidly. Results: The median age of the patients was 34 years (range, 27 to 45). Mean arterial blood pressure was 97 ${\pm}$ 10 mmHg at the time of biopsy. The median follow-up period was 85 months (range, 60 to 114). Kaplan-Meier analysis showed significant prognostic predictions for M, E, and T lesions. A Cox proportional hazard regression analysis also revealed prognostic predictions for E and T lesions. Conclusions: Using the Oxford classification in IgAN, E, and T lesions predicted renal outcome in Korean adults after taking clinical variables into account.