Data Collection
AKI was identified by the presence of ICD-9 diagnosis codes of 584.5 (acute kidney failure with lesion of tubular necrosis), 584.6 (acute kidney failure with lesion of renal cortical necrosis), 584.7 (acute kidney failure with lesion of renal medullary necrosis), 584.8 (acute kidney failure with other specified pathological lesion in kidney), or 584.9 (acute kidney failure, unspecified) in any of the listed diagnoses. The identification of AKI using ICD-9 diagnosis code has a specificity of 98% but a sensitivity of 17% and are likely to capture a more severe spectrum of AKI, compared with KDIGO serum creatinine-based criteria.8,9
Clinical characteristics, treatments, and outcomes during hospitalization were identified using ICD-9 codes (Table S1). Clinical characteristics included age, sex, race, year of hospitalization, alcohol consumption, certain comorbidities (obesity, anemia, diabetes mellitus, hypertension, dyslipidemia, coronary artery disease, congestive heart failure, atrial flutter/fibrillation, chronic kidney disease, and cirrhosis), and acute conditions (sepsis, volume depletion, seizure, gastrointestinal bleeding, ventricular arrhythmia/cardiac arrest). Treatments included gastric lavage, non-invasive and invasive mechanical ventilation, blood component transfusion, and renal replacement therapy. Outcomes included end-organ failure (respiratory, circulatory, liver, neurological or hematological failures), and in-hospital mortality. Resource utilization included length of hospital stay and hospitalization cost.