Figure 1. Formation of the Derivation, Internal Validation, and External Validation Cohorts Hospitalized With Acute Kidney Injury.

^aPatients without prehospitalization serum creatinine measurements were excluded from the study (49 patients of 2946 [1.6%] had advanced chronic kidney events from the Alberta source population).

^bTo ascertain whether patients had advanced chronic kidney disease, the first estimated glomerular filtration rate (eGFR) of less than 30 mL/min/1.73 m² was obtained a median of 75 days (interquartile range [IQR], 40-160 days) after discharge and the last a median of 267 days (IQR, 125-321 days) after discharge in the derivation and internal validation cohorts. There were 29 patients (0.2%) in the derivation and internal validation cohorts with only 1 eGFR less than 30 mL/min/1.73 m² and did not have a subsequent measurement during follow-up. They were not considered to have developed advanced chronic kidney disease. Patients were followed up through March 2015.