Prognostication of 90-day Kidney Function Recovery in Dialysis-Dependent Acute Kidney Injury from Outpatient...

Prognostic uncertainty regarding kidney function recovery for individuals with acute kidney injury receiving outpatient dialysis (AKI-D) may delay appropriate care (e.g., placement of permanent dialysis access). Accordingly, we developed and internally validated a prediction model prognosticating recovery in dialysis-dependent AKI at 90 days from time of outpatient dialysis initiation.

Using a national cohort of 2,544 incident outpatient in-center hemodialysis patients with AKI-D, we developed and internally validated a multivariable Cox proportional hazards model. The primary outcome was kidney function recovery to dialysis independence within 90 days of outpatient dialysis initiation. Candidate predictor variables included demographic, clinical, laboratory, and dialysis characteristics readily available in the electronic health record as part of usual outpatient dialysis care. We derived a parsimonious model using backward stepwise selection. Uniform shrinkage was employed to mitigate overfitting. Model performance was assessed through calibration and discrimination measured by Uno's C-index. Internal-external cross validation was employed to evaluate model performance and generalizability across geographic regions.

Among 2,544 individuals with AKI-D, 776 patients (cumulative incidence 34%, 95% confidence interval [CI]: [32% - 36%]) recovered kidney function within 90-days of outpatient dialysis initiation with median time-to-recovery (IQR) of 30 (26, 33) days. Ten predictor variables were retained in the final model, with the three most important predictors of kidney function recovery being: 1) serum creatinine; 2) interdialytic weight change; and 3) male sex. Internal-external cross validation suggested good generalizability across the geographical regions. The optimism-corrected Uno's C-index was 0.69 (95% CI, 0.67-0.71), with good calibration across regions.

We developed and internally validated a multivariable Cox proportional hazards model that prognosticates 90-day kidney function recovery among patients with AKI-D in the first week of outpatient dialysis. Model performance measures were acceptable despite relying solely on predictor variables available as part of usual outpatient dialysis care.