Table 1.

Definitions of AKI by data source

Type of ReviewDefinitionHospitalization Sample Size (n)
ICD-9-CM review
 AKI billing codes584.x (ICD-9-CM) or N17.x (ICD-10-CM) in any position34,179
Chart reviewa
 AKIcr50% change from outpatient sCr, or ≥0.5-mg/dl increase if peak sCr is >4 mg/dl, or 0.3-mg/dl increase in ≤48 hr, or AKI mention and initiation of RRT546
Electronic medical record reviewb
 AKIcr50% change from outpatient sCr, or ≥0.5-mg/dl increase if peak sCr is >4 mg/dl, or 0.3-mg/dl increase in ≤48 hr1970
 AKIcr_uopOutpatient baseline definition above or urine output <20 ml/hr×24 hr1839
  • ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification; ICD-10-CM, International Classification of Diseases, Tenth Revision, Clinical Modification; AKIcr, AKI by the creatinine-based criteria; sCr, serum creatinine; AKIcr_uop, AKI by the creatinine- or urine output–based criteria.

  • a Baseline sCr was taken as prehospitalization sCr when available, determined from (in order of preference): nephrology consult, admission or discharge note, or lowest inpatient serum creatinine (if judged adequate by adjudicating physician)

  • b Outpatient baseline defined as average outpatient serum creatinine 10–365 days before admission (15); ESRD cases (determined by linkage with US Renal Data System) were not considered AKI regardless of change in creatinine of urine output.