IgA Nephropathy: Correlation of WHO Classification and Morphologic Semi-quantitative Scoring System

Abstract

Background : IgA nephropathy (IgAN) is the most common glomerulonephritis worldwide, and the clinical course of IgAN shows marked variability. Many efforts have made to histologically predict the clinical outcome. There are two methods to classify IgAN. One is mainly based on the glomerular changes, such as the WHO and the Lee and Haas classification systems. The other is a morphologic semi-quantitative scoring system, which counts the changes of the glomerular, tubulointerstitial and vascular structures, respectively. The purpose of this study is to determine whether the WHO classification properly reflects the various morphologic findings of IgAN. Methods : We analyzed 354 cases of IgAN by both the WHO classification system and the semiquantitative scoring system and evaluated the correlations of these two methods. Results : The severity of the glomerular lesions (glomerulosclerosis, capsular adhesion and mesangial matrix expansion) and the tubulointerstitial lesions (interstitial fibrosis, tubular atrophy and interstitial lymphocytic infiltration) are strongly correlated with the increase of the WHO classes of IgAN (Spearman’s rho [R] ≥0.5, p<0.05). There is a weak correlation between crescent formation and the increase of the WHO classes (R=0.3, p<0.05). Conclusions : This study shows that the WHO classification well reflects the severity of various morphologic findings and this suggests a complementary role for the semi-quantitative scoring system in classifying IgAN.