Delta corticomedullary apparent diffusion coefficient on MRI as a biomarker for prognosis in IgA nephropathy

Objectives To explore the association of the cortico-medullary difference in apparent diffusion coefficient (ΔADC) with clinicopathological parameters of disease activity at the time of biopsy, and with the prognositic risk stratification in IgA nephropathy (IgAN) patients.Methods We included 112 patients with biopsy-proven IgAN who measured ΔADC. Patients underwent a kidney biopsy and diffusion-weighted magnetic resonance imaging within one week of the biopsy. Clinicopathological characteristics were compared according to different ΔADC levels. The effect of ΔADC on eGFR and kidney fibrosis was explored using multivariate regression and ROC analysis. An individual’s 5-year risk probability of progressing to ESKD or decreasing of eGFR > 50% was calculated by the guidelines-recommended international risk-prediction tool in IgAN. The effect of ΔADC on prognostic risk stratification was assessed. Net reclassification improvement (NRI) was used to evaluate the model performance.Results The average ΔADC was 168.89 ± 85.1 x10−6 mm2/s. ΔADC levels decreased significantly with increasing chronic kidney disease (CKD) stages (p = 0.0038). Spearman correlation analysis revealed that ΔADC was positively correlated with eGFR, hemoglobin, serum albumin, while negatively correlated with levels of serum creatine (Scr), blood urea nitrogen (BUN), T score of Oxford classification and Lee grades (p 167.1 × 10−6 mm2/s) in a fully-adjusted model. And reclassification analyses confirmed that the final adjusted model improved NRI.Conclusions ΔADC was significantly associated with kidney function and enabled a reliable evaluation of kidney IF severity in IgAN patients. Low ΔADC can predict a high 5-year kidney progression risk in IgAN, independent of important clinical factors. Moreover, the predictive ability to identify patients at high risk of severe kidney fibrosis and adverse progression estimates with satisfactory accuracy, facilitating ΔADC a promising and noninvasive tool in complementarily evaluating disease activity and the prognostic risk stratification in patients with IgAN.