Individuals who meet acute kidney injury (AKI) criteria in the community may not always require hospitalization, but they remain at high risk of poor long-term outcomes, according to a new study.

Simon Sawhney, MBBS, of the University of Aberdeen, U.K., and colleagues studied a cohort of 50,835 individuals, applying the NHS England AKI “e-alerts” based on Kidney Disease: Improving Global Outcomes (KDIGO) criteria to identify and follow 3 AKI groups: individuals with hospital-acquired AKI (HA-AKI); individuals with community-acquired AKI hospitalized within 7 days (CAA-AKI); and individuals with community-acquired AKI not hospitalized within 7 days (CANA-AKI). The researchers compared 30-day, 1- and 5-year mortality, 90-day renal recovery, and need for chronic renal replacement therapy (RRT). The researchers defined the start of an AKI episode as the first blood test meeting AKI criteria.

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AKI developed in 4,550 patients (9%). Of these, 2,779 (61.1%) were in the HA-AKI group, 1,042 (22.9%) in the CAA-AKI group, and 729 (16%) in the CANA-AKI group. The 30-day mortality rates were similar for the HA-AKI and CAA-AKI groups (24.2% and 20.2%, respectively), but significantly lower for the CANA-AKI group (2.6%), Dr. Sawhney’s team reported online ahead of print in Nephrology Dialysis Transplantation. Five-year mortality rates followed a similar pattern: 67.1%, 64.7%, and 46.2%, respectively.

Compared with the CAA-AKI group, those in the CANA-AKI group had significantly higher rates of renal non-recovery at 90 days (11.8% vs. 3.5%) and chronic RRT at 5 years (3.7% vs. 1.2%).

In addition, CANA-AKI patients were much less likely to undergo repeat testing at 7 days and 90 days. At 7 days, 81.7% of CANA-AKI patients did not have repeat testing compared with 18.6% and 20.4% of the HA-AKI and CAA-AKI groups, respectively. At 90 days, the proportions were 31%, 10.8%, and 14.1%, respectively.

“Despite AKI frequently initiating in the community, and despite the need for early recognition of of AKI, this is the first large population-based study to explore the implications of applying the same systematic AKI criteria to patients both admitted and not admitted within 7 days,” the authors noted.

Dr. Sawhney and his colleagues commented that the high rate of chronic RRT and lack of repeat testing in the CANA-AKI group was unexpected. “One explanation could be misclassification of rapidly progressing CKD patients when the AKI criteria are applied outside the hospital setting,” they stated. The low 30-day mortality might also suggest a less “acute” insult in CANA-AKI, according to the investigators.

Patients in the HA-AKI group were significantly older than those in the CAA-AKI and CANA-AKI groups (median age 77 years vs. 73 and 72 years, respectively). The proportion of patients aged 70 years and older was 71.8% in the HA-AKI group compared with 58.2% and 56% in the CAA-AKI and CANA-AKI groups, respectively.