Histological grading of IgA nephropathy predicting renal outcome: revisiting H. S. Lee's glomerular grading system

Background. The glomerular grading system is useful to compare biopsy specimens and to predict the natural course of disease in IgA nephropathy (IgAN), although no grading system can be perfect. Methods. H. S. Lee's grading system for IgAN was refined as follows: grade I, normal or focal mesangial cell proliferation; grade II, diffuse mesangial cell proliferation, or 75% of glomeruli with Cr/SS/GS. This refined H. S. Lee grading system was then tested for clinical relevance on 187 patients with IgAN followed up for an average of 6.5 years (minimum, 3 years). In the survival analysis, a modified primary end-point (progressive renal disease) was used. Results. The glomerular grades were significantly related to hypertension, serum creatinine levels and the amounts of proteinuria at time of biopsy. By univariate analysis, glomerular grades, hypertension, renal insufficiency and significant proteinuria (≥1 g/day) were significantly associated with progressive renal disease. By multivariate analysis using the Cox regression model, glomerular grades, renal insufficiency and significant proteinuria were independent prognostic factors for progressive renal disease. At the end of follow-up, glomerular grades were significantly related to serum creatinine levels, amounts of proteinuria, hypertension and progressive renal disease. Conclusions. These findings indicate that the refined H. S. Lee grading system for IgAN is useful in assessing the patients’ clinical outcome and is sufficiently simple and easy to reproduce as to be universally applicable in prognostic work.