Background AKI has been associated with increased mortality rate among VLBW infants. The best creatinine-based definition for AKI is still unclear. Our aim was to correlate mortality and different AKI-definitions.
Methods From January 1st 2005 to December 31st 2011 all VLBW infants born at S. Gerardo Hospital were recruited whenever ≥2 consecutive p-creatinine determined within 48 hours between 3 and 15 days of life were available.
AKI was defined as single creatinine ≥1.5 mg/dl (AKI-1), increase of ≥0.3 mg/dl within 48h (AKI-2) or increase of ≥50% within 48h (AKI-3).
The statistical concordance between the definitions was evaluated using the Cohen’s Kappa coefficient and their association with mortality using uni- and multivariable logistic regression. AKI-definitions were adjusted for each other and for GA, BW and Apgar score.
Results Among 263 VLBW infants, 28 (10.6%), 40 (15.2%) and 26 (9.9%) met the definition for AKI-1, AKI-2 and AKI-3 respectively. Low agreement was shown between AKI-1/AKI-2 (Kappa 0.43, 95%CI:0.27–0.59) and AKI-1/AKI-3 (Kappa 0.32, 95%CI:0.14–0.51). Substantial agreement was observed for AKI-2/AKI-3 (Kappa 0.69, 95%CI:0.56–0.82).
68/263 patients died (28.8%), with AKI-1 45.1%, AKI-2 32.5% and AKI-3 26.9% respectively.
AKI patients run higher risk of death than the others (Crude OR 13.6 [P<0.001], 6.7 [P<0.001] and 3.8 [P0.007] for AKI-1, AKI-2 and AKI-3).
Using multivariable model, AKI-1 and AKI-2 remained associated with higher mortality (OR 4.25 [P=0.008] and OR 3.70 [P=0.041]).
Conclusions Different AKI-definitions lead to substantially different patients classifications. Even minimal increment of creatinine are associated with augmented risk of death among VLBW infants.