Community-acquired acute kidney injury (CA-AKI) is AKI that develops outside of the hospital setting. The causes of CA-AKI are thought to be heterogeneous and can include volume depletion due to poor oral intake, urinary obstruction, or exposure to nephrotoxic medications.
According to Clarissa J. Diamantidis, MD, MHS, and colleagues, there are no standard definitions for detection of AKI outside of the acute hospital setting. They also note that because accurate measurement of kidney function requires the availability of serial creatinine laboratory values, the detection of reduction of kidney function outside of the acute hospital setting is difficult.
Using laboratory and administrative data from the Veterans Health Administration (VA), the researchers conducted a retrospective cohort study to quantify the incidence of CA-AKI among VA primary care users between 2013 and 2017 and to identify the patient factors associated with the risk of developing CA-AKI. Results were reported in the American Journal of Kidney Diseases [2023;82(3):300-310].
Eligible study participants were VA primary care users from 2013 to 2017 who had recorded outpatient serum creatinine measurement and no history of chronic kidney disease (CKD) stage 5 or end-stage kidney disease. The study predictors were sociodemographics, comorbidities, medication use, and health care utilization.
The outcome of interest was annual incidence of CA-AKI defined as a ≥1.5-fold relative increase in serum creatinine on either a subsequent outpatient serum creatinine measurement or inpatient serum creatinine measurement obtained within ≤24 hours of hospital admission. Index serum creatinine was defined as the preceding outpatient serum creatinine ≥24 hours apart and ≤12 months from the outcome serum creatinine in each cohort year.
The cohort included 5,375,435 distinct US veterans contributing 14,129,977 veteran-years of observation among VA primary care users between 2013 and 2017. There were approximately 2.5 million veterans in the 2013 to 2015 cohort, 2.9 million in the 2016 cohort, and 3.5 million in the 2017 cohort.
The mean age of the overall cohort was 63 years, most (92%-93%) were male, and 75% were White. More than half lived in urban settings, and the median driving distance to the nearest VA facility was 11 miles. Median estimated glomerular filtration rate (eGFR) was 82 mL/min/1.73 m2 and approximately 7% had a diagnosis code for CKD.
More than 30% had diabetes, and 63% had hypertension. Approximately 30% had a prescription for a proton-pump inhibitor, 38% for a nonsteroidal anti-inflammatory drug, 26% for a diuretic, and 40% for a renin-angiotensin-aldosterone system (RAAS) blocker. In the year prior, approximately half of all veterans had zero hospital days and six outpatient encounters per year, and approximately 1% had a nephrology encounter.
The cumulative incidence of CA-AKI was approximately 1.9% per year. Overall, 26.9% of CA-AKI was detected at hospital admission. Seventy-nine percent of CA-AKI was stage 1, 15% was stage 2, and 6% was stage 3. In 29.7% of veterans, a diagnosis code for AKI was detected; 69.4% of inpatient CA-AKI at hospital admission had a documented diagnosis, and 14.5% of outpatient CA-AKI cases reported this diagnosis. Results of a post hoc analysis examining the frequency of repeated episodes of CA-AKI demonstrated that only 8% of veterans (n=18,630) had an observed repeat of AKI during the study period.
There were associations between higher risk of CA-AKI and eGFR <15 mL/min/1.73 m2 (hazard ratio [HR], 2.70; 95% CI, 2.32-3.14), higher levels of outpatient health care utilization (HR, 2.38; 95% CI, 2.31-2.46), female sex (HR, 1.26; 95% CI, 1.24-1.28), or other/missing rural residence (HR, 1.37; 95% CI, 1.27-1.47). Medications associated with a higher risk of CA-AKI were RAAS blockers (HR, 1.45; 95% CI, 1.44-1.47) and diuretics (HR, 1.33; 95% CI, 1.32-1.34).
There were numerous comorbidities associated with increased risk of CA-AKI: metastatic cancer (HR, 1.93; 95% CI, 1.88-1.98), HIV/AIDS (HR, 1.84; 95% CI, 1.77-1.91), diabetes (HR, 1.48; 95% CI, 1.47-1.50), alcohol or drug use disorder (HR, 1.42; 95% CI, 1.40-1.44), liver disease (HR, 1.41; 95% CI, 1.39-1.43), heart failure (HR, 1.37; 95% CI, 1.35-1.39), sickle cell anemia (HR, 1.30; 95% CI, 1.03-1.64), kidney stones (HR, 1.31; 95% CI, 1.28-1.34), cancer (HR, 1.27; 95% CI, 1.25-1.28), weight loss (HR, 1.24; 95% CI, 1.21-1.28), hypertension (HR, 1.23; 95% CI, 1.21-1.25), and tobacco use (HR, 1.19; 95% CI, 1.18-01.21).
There was an association between acute myocardial infarction and a lower hazard of CA-AKI (HR, 0.81; 95% CI, 0.78-0.84).
In a sensitivity analysis that limited the analytic cohort to veterans with two or more serum creatinine measures (n=12,062,827), the annual incidence of CA-AKI was approximately 2.1% in all cohort years, with the exception of 2017 when it was 1.8%. There were no significant changes in the factors associated with incidence of CA-AKI.
In citing limitations to the study, the authors included using data from the VA, limiting the generalizability to other populations that have a higher proportion of females; the lack of a standardized definition of CA-AKI; and assessing medication use at a single time point.
In summary, the researchers said, “CA-AKI affects one of every 50 primary care users in the VA. The majority of CA-AKI events occurred in the outpatient setting, so studies on AKI in the hospital likely dramatically underestimate the true incidence of CA-AKI. Under-recognition of CA-AKI represents a missed opportunity to prevent and manage the long-term consequences of CA-AKI. Therefore, comprehensive investigations using longitudinal health data are critically needed to determine the impact of CA-AKI on long-term clinical outcomes in the US population.”
Takeaway Points
- Researchers reported results of a retrospective cohort study designed to estimate the incidence and risk factors of community-acquired acute kidney injury (CA-AKI).
- Using data from the Veterans Health Administration, the analysis demonstrated a cumulative incidence of CA-AKI of approximately 2.1% annually.
- Factors associated with increased risk of CA-AKI included high health care utilization, female sex, chronic illness, cancer, rural location, and use of renin-angiotensin-aldosterone system inhibitors or diuretics.
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