KIDNEY DISEASES 17 Original Paper Iranian Journal of Kidney Diseases | Volume 10 | Number 1 | January 2016 Validation of Oxford Classification of Immunoglobulin A Nephropathy An Iranian Experience Alireza Sadeghipour, 1 Alireza Hendi, 2 Mojgan Asgari, 3 Masoud Sotoudeh, 4 Mahmoud Parvin, 5 Irina Filip, 6 Amir Radfar, 7 Pegah Babaheidarian 1 Introduction. In 2009, the Oxford classification of immunoglobulin A (IgA) nephropathy was proposed by the working group of the International IgA Nephropathy Network and Renal Pathology Society. It established specific pathologic features that predict the risk of progression of disease. This study aimed to evaluate the interobserver reproducibility of the Oxford classification of IgA nephropathy between Iranian nephropathologists. Materials and Methods. We included 100 patients with primary IgA nephropathy diagnosed between 2001 and 2011. Histologic slides were circulated among 4 pathologists. A score sheet was answered by each individual pathologist for each biopsy, according to the instruction of the Oxford classification. Reproducibility was determined for each variable, using intraclass correlation coefficient (ICC). Results. The ICC values calculated for each major category of the Oxford classification were as follows: the highest score of 0.94 for tubular atrophy and interstitial fibrosis; 0.8 for glomerular basement membrane duplication, extracapillary proliferation, and segmental endocapillary proliferation; and 0.1 to 0.3 for arterial lesions, especially for hyalinosis of arterioles and intimal thickening of arcuate vessels and interlobar arteries. Conclusions. The Oxford classification of IgA nephropathy is a useful tool and evidenced-based method with high interobserver reproducibility in pathology reporting. Our data suggest that Oxford classification may be used as a model for classification of other renal pathologies in the future. IJKD 2016;10:17-21 www.ijkd.org 1 Department of Pathology, Rasoul Akram Hospital, Iran University of Medical Sciences, Tehran, Iran 2 Department of Pathology, Golestan University, Gorgan, Iran 3 Department of Pathology Hasheminejad Nejad hospital, Iran University of Medical Sciences, Tehran, Iran 4 Department of Pathology, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran 5 Department of Pathology, Labbafi-Nejad Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran 6 Kaiser Permanente, Fontana, California, USA 7 AT Still University, Mesa, Arizona, USA Keywords. IgA nephropathy, Oxford classification, Interobserver reproducibility INTRODUCTION Immunoglobulin A (IgA) nephropathy is among the most common primary forms of glomerulonephritis. Patients have different clinical courses and progression to end-stage renal disease takes place in 20% of the cases in 10 consecutive years. 1 As such, it is crucial to diagnose the disease in its early stages of progression when the therapeutic intervention is still effective. 2-5 Histologically, IgA nephropathy is diagnosed by deposition of IgA-dominant or IgA-codominant immune complexes within glomeruli, shown by immunofluorescence or immunohistochemistry. 6-8 In 2009, the working group of the International IgA Nephropathy Network and the Renal Pathology Society introduced for the first time