Incidence and Prognosis of Acute Kidney Diseases and Disorders Using an Integrated Approach to Laboratory Measurements in a Universal Health Care System

Abstract

Importance: Abnormal measurements of kidney function or structure may be identified that do not meet criteria for acute kidney injury (AKI) or chronic kidney disease (CKD) but nonetheless may require medical attention. The Kidney Disease: Improving Global Outcomes Clinical Practice Guideline for AKI proposed criteria for the definition of acute kidney diseases and disorders (AKD), which include AKI; however, the incidence and prognosis of AKD without AKI remain unknown.

Objective: To characterize the incidence and outcomes of AKD without AKI, with or without CKD.

Design, setting, and participants: Retrospective cohort study including all adult residents in a universal health care system in Alberta, Canada, without end-stage kidney disease (ESKD) and with at least 1 serum creatinine measurement between January 1 and December 31, 2008, in a community or hospital setting. Data analysis took place in 2018.

Main outcomes and measures: The Kidney Disease: Improving Global Outcomes guideline definitions for CKD, AKI, and AKD based on serum creatinine, estimated glomerular filtration rate, and albuminuria criteria were applied to estimate the proportion of patients with CKD, AKI, and AKD without AKI, and combinations of the conditions. Patients were followed up for up to 8 years (study end date, June 31, 2016) to characterize their risks of mortality, development of new CKD, progression of preexisting CKD, and ESKD.

Results: Among 1 109 099 Alberta residents included in the cohort, the mean (SD) age was 52.3 (17.6) years, and 43.0% were male. Findings showed that AKD without AKI was common (3.8 individuals without preexisting CKD and 0.6 with preexisting CKD per 100 population tested). In Cox proportional hazards and competing risks models over a median (interquartile range) of 6.0 (5.7-6.3) years of follow-up, AKD without AKI (compared with no kidney disease) was associated with higher risks of developing new CKD (37.4% vs 7.4%%; adjusted sub-hazard ratio [sHR], 3.17; 95% CI, 3.10-3.23), progression of preexisting CKD (49.5% vs 34.6%; adjusted sHR, 1.38; 95% CI, 1.33-1.44), ESKD (0.6% vs 0.1%; adjusted sHR, 8.56; 95% CI, 7.32-10.01), and death (25.8% vs 7.3%; adjusted hazard ratio, 1.42; 95% CI, 1.39-1.45).

Conclusions and relevance: Criteria for AKD identified many patients who did not meet the criteria for CKD or AKI but had overall modestly increased risks of incident and progressive CKD, ESKD, and death. The clinical importance of AKD remains to be determined.

Figure 1.. Percentage of Adult Residents of Alberta, Canada, With Chronic Kidney Disease (CKD), Acute Kidney Injury (AKI), Acute Kidney Diseases and Disorders (AKD), and Combinations of These Conditions in 2008

Conditions were identified by testing for serum creatinine, estimated glomerular function rate, and albuminuria.

Figure 2.. Cumulative Incidence Curves for Mortality, Incident Chronic Kidney Disease (CKD), Progressive CKD, and End-Stage Kidney Disease (ESKD), According to Kidney Disease Classification of Residents of Alberta, Canada, Who Received Serum Creatinine Testing in 2008

The cumulative incidence curves of mortality were plotted using the Kaplan-Meier function. The curves for other outcomes were plotted using the cumulative incidence function. Note that the y-axis scale varies by outcome. AKD indicates acute kidney diseases and disorders; AKI, acute kidney injury; and NKD, no kidney disease.