Epidemiology and outcomes in community-acquired versus hospital-acquired AKI

Abstract

Background and objective: Compared with AKI in hospitalized patients, little is known about patients sustaining AKI in the community and how this differs from AKI in hospital. This study compared epidemiology, risk factors, and short- and long-term outcomes for patients with community-acquired (CA) and hospital-acquired (HA) AKI.

Design, setting, participants, & measurements: A total of 15,976 patients admitted to two district general hospitals between July 11, 2011, and January 15, 2012 were studied. Through use of an electronic database and the AKI Network classification, 686 patients with CA-AKI and 334 patients with HA-AKI were identified. Patients were followed up for 14 months, and data were collated on short-term and long-term renal and patient outcomes.

Results: The incidence of CA-AKI among all hospital admissions was 4.3% compared with an incidence of 2.1% of HA-AKI, giving an overall AKI incidence of 6.4%. Patients with CA-AKI were younger than patients with HA-AKI. Risks for developing HA and CA-AKI were similar and included preexisting CKD, cardiac failure, ischemic heart disease, hypertension, diabetes, dementia, and cancer. Patients with CA-AKI were more likely to have stage 3 AKI and had shorter lengths of hospital stay than patients with HA-AKI. Those with CA-AKI had better (multivariate-adjusted) survival than patients with HA-AKI (hazard ratio, 1.8 [95% CI, 1.44-2.13; P<0.001] for HA-AKI group). Mortality for the CA-AKI group was 45%; 43.7% of these deaths were acute in-hospital deaths. Mortality for the HA-AKI group was 62.9%, with 68.1% of these deaths being acute in-hospital deaths. Renal referral rates were low across the cohorts (8.3%). Renal outcomes were similar in both CA-AKI and HA-AKI groups, with 39.4% and 33.6% of patients in both groups developing de novo CKD or progression of preexisting CKD within 14 months, respectively.

Conclusion: Patients with CA-AKI sustain more severe AKI than patients with HA-AKI. Despite having risk factors similar to those of patients with HA-AKI, patients with CA AKI have better short- and long-term outcomes.

Keywords: acute renal failure; chronic kidney disease; clinical nephrology.

Figure 1.

In-hospital outcomes: community- versus hospital-acquired AKI. The graph demonstrates the percentage of AKI episodes that showed recovery/death/progression of CKD, that were unrecognized, or that occurred in patients discharged on RRT following AKI. The numbers at the top of the individual bars reflect the actual numbers of AKI episodes within this group. P values were calculated using Pearson chi-squared test/Fisher exact test where appropriate. ⁺Unrecognized renal impairment, defined as a discharge from the hospital with worsening renal impairment without acknowledgment in discharge letter or follow-up planned. *Figures for inpatient (IP) deaths include those who died with AKI and those who had recovered from an AKI episode but died subsequently.

Figure 2.

Kaplan–Meier survival statistics comparing community-acquired AKI (CA-AKI) and hospital-acquired AKI (HA-AKI) groups. P<0.001 for all comparisons. Numbers of patients at risk at each time point shown below the graph.

Figure 3.

Long-term mortality outcomes according to AKI stage. The graph demonstrates percentages of patients in each AKI stage who died within 14 months. P=0.001 for comparisons between death in AKI stage 1 (Pearson chi-squared test). AKI stages 2 and 3 mortality comparisons between community-acquired (CA) AKI and hospital-acquired (HA) AKI groups not significant.