Validation study on the international and domestic histological classifications of IgA nephropathy

在日本，由卫生、劳动和福利大臣组织的进行性肾脏疾病研究委员会的IgAN特别研究小组最近制定了基于证据的IgAN临床病理分类（J Nephrol 2013）。另一方面，IgA肾病的国际组织学分类已经发展起来，可以比较不同种族和世代之间的组织学特征（Kidney Int. 2009）。这两种分类并不相同。因此，国际牛津分类可能需要进一步完善才能成为国际标准。本研究的目的是根据产生牛津分类的研究使用的方法来验证牛津分类，并在回顾性分析中将日本受试者的结果与牛津研究的结果进行比较。对233名日本成人IgAN患者进行了顺序临床数据和肾脏活检，随访时间中位数为110个月。我们的研究表明，牛津和日本两种分类之所以不相同，是因为所选择的与肾功能下降相关的组织学参数受到不同随访期、不同世代和不同纳入标准的强烈影响。从这个角度来看，一个世界性的组织学分类标准应该更加灵活，以适用于不同的特定人群。因此，组织学分类应该是一个分裂的系统，由所有病理参数组成。

In Japan, the Special IgAN Study Group of the Progressive Renal Diseases Study Committee was organized by the Minister of Health, Labor and Welfare and has recently developed an evidence-based clinicopathological classification of IgAN(J Nephrol 2013). On the other hand, the international histological classification of IgA nephropathy has been developed, which enables comparison of histological characteristics among ethnicities and generations (Kidney Int. 2009).These 2 classifications were not identical. Therefore, the international Oxford classification may require further refinement to become an international standard. The purpose of this study was to validate the Oxford classification following the method used by the study producing Oxford classification and to compare the results of Japanese subjects with those of the Oxford study in a retrospective analysis. Sequential clinical data as well as renal biopsies were obtained from 233 Japanese adults with IgAN were followed for a median of 110 months.Our study suggested that the reason why the 2 classifications, the Oxford and Japanese classification, were not identical, depends on that the selected histological parameters, which were associated with renal function decline, were strongly influenced by different followed-up period, different generations, and different inclusion criteria. From this point of view, a worldwide standard of histological classification should be more flexible for application to different specific cohorts. Therefore, the histological classification should be a split system, which composed of all pathological parameters.