Prognostic robustness of serum creatinine based AKI definitions in patients with sepsis: a prospective cohort study

Abstract

Background: It is unclear how modifications in the way to calculate serum creatinine (sCr) increase and in the cut-off value applied, influences the prognostic value of Acute Kidney Injury (AKI). We wanted to evaluate whether these modifications alter the prognostic value of AKI for prediction of mortality at 3 months, 1 and 2 years.

Methods: We prospectively included 195 septic patients and evaluated the prognostic value of AKI by using three different algorithms to calculate sCr increase: either as the difference between the highest value in the first 24 h after ICU admission and a pre-admission historical (ΔHIS) or an estimated (ΔEST) baseline value, or by subtracting the ICU admission value from the sCr value 24 h after ICU admission (ΔADM). Different cut-off levels of sCr increase (0.1, 0.2, 0.3, 0.4 and 0.5 mg/dl) were evaluated.

Results: Mortality at 3 months, 1 and 2 years in AKI defined as ΔADM > 0.3 mg/dl was 48.1 %, 63.0 % and 63.0 % vs 27.7 %, 39.8 % and 47.6 % in no AKI respectively (OR(95%CI): 2.42(1.06-5.54), 2.58(1.11-5.97) and 1.87(0.81-4.33); 0.3 mg/dl was the lowest cut-off value that was discriminatory. When AKI was defined as ΔHIS > 0.3 mg/dl or ΔEST > 0.3 mg/dl, there was no significant difference in mortality between AKI and no AKI.

Conclusions: The prognostic value of a 0.3 mg/dl increase in sCr, on mortality in sepsis, depends on how this sCr increase is calculated. Only if the evolution of serum creatinine over the first 24 h after ICU admission is taken into account, an association with mortality is found.

Fig. 1

Illustration of the method used for study inclusion. a: Graphic presentation of the time interval between the sCr value at D1 and the ICU admission value in case of a patient being admitted just after 18 pm. b: Graphic presentation of the time interval between the sCr value at D1 and the ICU admission value in case of a patient being admitted just before 18 pm

Fig. 2

Evolution of serum creatinine over 4 days in patients with Acute Kidney Injury (AKI), according to different algorithms. As opposed to Acute Kidney Injury based on ΔADM > 0.3 mg/dl (a), there is a steady decrease in serum creatinine after admission over the following four days when AKI is defined according to ΔHIS > 0.3 mg/dl (b) or ΔEST > 0.3 mg/dl (c)

Fig. 3

Mortality rates (%) in Acute Kidney Injury (AKI) vs no Acute Kidney Injury according to different algorithms, in the entire cohort and in ICU survivors separately. a: Mortality rates at ICU, 3 months, 1 year and 2 years in the entire cohort in AKI vs no AKI, either based on ΔADM > 0.3 mg/dl, ΔHIS > 0.3 mg/dl or ΔEST > 0.3 mg/dl. Only based on ΔADM > 0.3 mg/dl, there is a higher mortality at ICU, 3 months and 1 year in AKI vs no AKI. At year 2, there is no significant different in mortality between AKI and no AKI with either of the algorithms. b: Mortality rates at 3 months, 1 year and 2 years in ICU survivors in AKI vs no AKI, either based on ΔADM > 0.3 mg/dl, ΔHIS > 0.3 mg/dl or ΔEST > 0.3 mg/dl. There is no significant difference in mortality between AKI and no AKI at the three time points, independent of the algorithm used

Fig. 4

Odds ratio of incremental cut-off values for serum creatinine increase and mortality in the entire cohort. A 0.3 mg/dl increase in serum creatinine is the lowest robust cut-off value associated with 3 months mortality (a), but only if this increase is based on ΔADM > 0.3 mg/dl (OR 2.42(1.06-5.54). At year 1 (b) and year 2 (c), a serum creatinine increase of 0.3 mg/dl is also the lowest robust cut-off value associated with mortality but again only if this increase is based on ΔADM > 0.3 mg/dl (RR 2.11(1.24-3.6) and RR 1.79(1.06-3.03) at year 1 and year 2 respectively)