Temporal trends in acute kidney injury across health care settings in the Irish health system: a cohort study

Abstract

Background: Complete ascertainment of the true rates of acute kidney injury (AKI) and emerging trends are essential for planning of preventive strategies within health systems.

Methods: We conducted a retrospective cohort study from 2005 to 2014 using data from regional laboratory information systems to determine incidence rates of AKI and severity Stages 1-3 in the Irish health system. Multivariable models were developed to explore annual trends and the contributions of demographic factors, clinical measures, geographic factors and location of medical supervision expressed as adjusted odds ratios (ORs) and 95% confidence intervals (CIs).

Results: From 2005 to 2014, incidence rates of AKI increased from 6.1% (5.8-6.3) to 13.2% (12.7-13.8) per 100 patient-years in men and from 5.0% (4.8-5.2) to 11.5% (11.0-12.0) in women, P < 0.001. Stage 1 AKI accounted for the greatest growth in incidence, from 4.4% (95% CI 4.3-4.6) in 2005 to 10.1% (95% CI 9.8-10.5) in 2014 (P < 0.001 for trend). Compared with 2005, patients in 2014 were more likely to experience AKI [OR 4.53 (95% CI 4.02-5.1) for Stage 1, OR 5.22 (4.16-6.55) for Stage 2 and OR 4.11 (3.05-5.54) for Stage 3], adjusting for changing demographic and clinical profiles. Incidence rates of AKI increased in all locations of medical supervision during the period of observation, but were greatest for inpatient [OR 19.11 (95% CI 17.69-20.64)] and emergency room settings [OR 5.97 (95% CI 5.56-6.42)] compared with a general practice setting (referent).

Conclusion: Incidence rates of AKI have increased substantially in the Irish health system, which were not accounted for by changing demographic patterns, clinical profiles or location of medical supervision.

Keywords: acute kidney injury, acute renal failure, AKI, epidemiology, surveillance.

FIGURE 1

A Strengthening the Reporting of Observational Studies in Epidemiology flow diagram to illustrate cohort construction. The final data set (n = 451 646) captured information on demographic characteristics, county of residence, primary location of patient supervision, laboratory measures of health status, dialysis indicator variables and death.

FIGURE 2

(a) Temporal trends in the incidence of AKI by sex in the health system. (b) Temporal trends in the incidence of AKI by age and sex in the health system. Dashed lines and error bars represent incidence rates with 95% CIs calculated from the direct method, whereas continuous lines and bands represent incident rates and 95% CIs calculated from Poisson regression.

FIGURE 3

(a) Temporal trends in the incidence rates of AKI by severity stage in the Irish health system. (b) Temporal trends in incidence rates of Stage 2 and Stage 3 AKI (magnified).

FIGURE 4

Adjusted OR for the first AKI event by the stage of AKI across calendar years in the Irish health system. The relationship between calendar year and the OR of AKI is modelled separately for AKI Stages 1–3 with year 2005 as the referent. In each model, covariates for adjustment include age, sex, baseline GFR estimated using the CKD-EPI equation, county of residence, location of medical supervision, laboratory measures of illness (haemoglobin, serum albumin, white blood cell count, serum potassium, serum calcium and serum phosphorus concentration) and calendar year. P < 0.001 for each year compared with referent 2005.

FIGURE 5

Temporal trends in the incidence of AKI by severity stage in the Irish health system. The solid line represents data from primary analysis and the dashed line represents data from the first sensitivity analysis.