Acute Kidney Injury in the Outpatient Setting Associates with Risk of End-Stage Renal Disease and Death in Patients with CKD

Current acute kidney injury (AKI) diagnostic criteria are restricted to the inpatient setting. We proposed a new AKI diagnostic algorithm for the outpatient setting and evaluate whether outpatient AKI (AKI(OPT)) modifies the disease course among patients with chronic kidney disease (CKD) enrolled in the national predialysis registry. AKI(OPT) was detected when a 50% increase in serum creatinine level or 35% decline in eGFR was observed in the 180-day period prior to enrollment in the predialysis care program. Outcomes were progression to end-stage renal disease (ESRD) and all-cause mortality. Association analyses were performed using multiple Cox regression and coarsened exact matching (CEM) analysis. Among 6,046 patients, 31.5% (1,905 patients) had developed AKI(OPT) within the 180-day period before enrollment. The adjusted hazard ratios of the 1-year and overall risk of ESRD among patients with preceding AKI(OPT) compared with those without AKI(OPT) were 2.61 (95% CI: 2.15–3.18) and 1.97 (1.72–2.26), respectively. For 1-year and overall risk of all-cause mortality, patients with AKI(OPT) had respectively a 141% (95% CI: 89–209%) and 84% (56–117%) higher risk than those without AKI(OPT). This statistical inference remained robust in CEM analysis. We also discovered a complete reversal in the eGFR slope before and after the AKI(OPT) from −10.61 ± 0.32 to 0.25 ± 0.30 mL/min/1.73 m(2) per year; however, the loss of kidney function is not recovered. The new AKI(OPT) diagnostic algorithm provides prognostic insight in patients with CKD.