Development and validation of a nomogram to predict kidney survival at baseline in patients with C3 glomerulopathy

Background C3 glomerulopathy is a rare and heterogeneous complement-driven disease. It is often challenging to accurately predict in clinical practice the individual kidney prognosis at baseline. We herein sought to develop and validate a prognostic nomogram to predict the long-term kidney survival. Methods Retrospective, multicenter observational cohort study in 35 nephrology departments belonging to the GLOSEN group. The dataset was randomly divided into training group (n = 87) and validation group (n = 28). The least absolute shrinkage and selection operator (LASSO) regression was used to screen the main predictors of kidney outcome, and used to build the nomogram. Accuracy of the nomogram was assessed by discrimination and risk calibration, in the training and validation sets. Results The study group comprised 115 patients, of whom 46 patients (40%) reached kidney failure in a median follow-up of 49 months (range 24–112). No significant differences were observed in baseline estimated glomerular filtration rate (eGFR), proteinuria or total chronicity score of kidney biopsy, between patients in the training versus those in the validation set. The selected variables by LASSO were eGFR, proteinuria and total chronicity score. Based on Cox model a nomogram was developed for the prediction of kidney survival at 1-, 2-, 5- and 10-years from diagnosis. The C-index of the nomogram was 0.860 (95% confidence interval 0.834–0.887), and calibration plots showed optimal agreement between predicted and observed outcomes. Conclusions We constructed and validated a practical nomogram with good discrimination and calibration, to predict the risk of kidney failure in C3G patients at 1-, 2-, 5- and 10-years.