Clinical value of the renal pathologic scoring system in complement-mediated thrombotic microangiopathy

OBJECTIVES: This study was initiated to establish a renal thrombotic microangiopathy (TMA) scoring system based on clinical needs and investigate its predictive value for patients’ long-term outcomes. METHODS: Kidney biopsy-proven Complement-mediated TMA (C-TMA) patients from January 2000 to December 2017 in Peking University First Hospital were retrospectively studied. Both acute and chronic TMA-related lesions, including 15 pathologic indices, were semiquantitatively scored. The interobserver and intraobserver reproducibility and correlation between the pathologic indices and clinical parameters were analyzed. Furthermore, the patients were divided into 2 groups by dialysis use at baseline, and the association of these pathologic indices with their prognostic outcomes was assessed between the two groups. RESULTS: Ninety-two patients with renal biopsy-proven C-TMA were enrolled. All fifteen included pathology indices showed good or moderate interobserver and intraobserver reproducibility and correlated well with several clinical parameters. Several clinicopathological indices were worse in the dialysis group than in the nondialysis group, such as serum creatinine, hemoglobin, platelet count, and estimated glomerular filtration rate. Moreover, morphologic features in the dialysis group presented with more severe vascular lesions. Interstitial fibrosis and chronic tubulointerstitial lesions were related to a trend of high risk of continuous dialysis in the dialysis group. Based on univariate and multivariable Cox regression analysis, more severe glomerular lesions, including glomerular mesangiolysis, glomerular basement membrane double contours and glomerular mesangial proliferation, were identified as risk factors predicting worse prognosis. CONCLUSIONS: Our renal C-TMA semiquantitative scoring system is reliable with good reproducibility and prognostic value in clinical practice, which needs further validation.