Effects of the diagnostic window and duration of acute kidney injury on 1-year mortality in elderly patients: a single-center retrospective study

Abstract

Background: We evaluated the prognostic impact of AKI duration on the 1-year mortality rate in elderly patients diagnosed based on the 48-hour and 7-day changes in serum creatinine (Scr) levels recommended by the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines.

Methods: This retrospective study was conducted from 2007 to 2018 on elderly patients in the Geriatric Department of the Chinese PLA General Hospital. Based on the two diagnostic criteria in the KDIGO guidelines, the patients were divided into a 48-hour diagnostic window and a 7-day diagnostic window group, and into transient AKI (lasting 1-2 days) and persistent AKI (lasting 3-6 days, and ≥ 7 days) based on the time at which the Scr level returned to the baseline value. The primary outcome was the 1-year mortality rate after AKI.

Results: In total, 688 patients were enrolled, including 367 (53.3%) with a 48-hour and 321 (46.7%) with a 7-day diagnostic window. Of the 688 patients, in the 48-hour window group, 12.0% had transient AKI, 31.1% had lasting 3-6 days, and 56.9% had lasting ≥ 7 days; in the 7-day window group, 5.3% had transient AKI, 24.0% had lasting 3-6 days, and 70.7% had lasting ≥ 7 days. Overall, 332 patients (33.6%) died within 1 year, including 189 (51.5%) in the 48-hour and 143 (44.5%) in the 7-day diagnostic window group. After adjusting for multiple covariates, AKI duration was associated with a significantly higher 1-year mortality rate (3-6 days: HR = 3.535; 95% CI = 1.685-7.417, P = 0.001; ≥ 7 days: HR = 2.400; 95% CI = 1.152-5.001, P = 0.019) in the 48-hour diagnostic window group, but it did not differ in the 7-day diagnostic window group (P = 0.452).

Conclusions: Persistent AKI was common in elderly hospitalized patients, accounting for 88% and 95% of patients with 48-hour and 7-day diagnostic windows, respectively. Moreover, AKI duration was associated with different clinical outcomes depending on the diagnostic window. Further studies should focus on the mechanism underlying the relationship of AKI outcomes with diagnostic criteria.

Keywords: 1-year mortality rate; Acute kidney injury; Diagnostic window; Duration; Risk factor.