Defining Acute Kidney Injury Using KDIGO Criteria

AKI was defined using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria based on a 1.5-fold increase in serum creatinine on enrollment from the estimated baseline. AKI was staged as follows: stage 1, 1.5–1.9-fold increase in creatinine over baseline; stage 2, 2.0–2.9-fold increase over baseline; and stage 3, ≥ 3.0-fold increase over baseline. AKI was classified as severe (severe AKI) if it was stage 2 or 3 [21 (link)]. Baseline creatinine was estimated using a previously validated height-independent approach assuming a GFR of 120 mL/min per 1.73m² as previously described [22 (link)]. The eGFR value was adjusted for the difference between estimated and measured GFR values by age using iohexol clearance. Adding a constant value of 16 to age-based norms across age groups was used to account for creatinine-based over-estimation of GFR [23 (link)]. Creatinine was tested using the modified Jaffe colorimetric method on an Alinity c instrument (Abbott, Lake Forest, IL) which is traceable to an isotope dilution mass spectrometry (IDMS) reference method.