E BROOKES1, R ROBBINS2, D ANTHONY POWER3
1St Vincent’s Hospital Melbourne, Fitzroy, Australia, 2The Data Analytics Research and Evaluation Centre, Austin Health and The University of Melbourne, Heidelberg, Australia, 3Austin Health, Heidelberg, Australia
Background: Elevated urea-to-creatinine ratio (UCR) is associated with increased risk of all-cause mortality in haemodialysis patients, but there are no studies to date in non-end-stage renal disease.
Aim: To assess the epidemiology of UCR among chronic kidney disease (CKD) hospital patients and determine the association between UCR level and inpatient clinical outcomes.
Methods: This retrospective cohort study (n = 11,156) included patients with an estimated glomerular filtration rate <60mL/min/1.73m² admitted to Austin Health between 2014 and 2019 and who had paired admission serum urea and creatinine values. Dialysis patients or those with a renal transplant were excluded. Multivariate logistic analysis was conducted to identify factors associated with elevated serum UCR (>100). Odds ratios for inpatient mortality, intensive care unit (ICU) admission, hospital readmission and hospital length of stay were calculated with multivariate regression adjusted for demographics, comorbidities and renal function.
Results: Elevated UCR was present in 27.67% of hospital admissions. Multivariate regression analysis revealed age ≥65 years, female gender, gastrointestinal tract bleeding, heart failure and hypovolaemia to be associated with higher risk of elevated UCR. Higher UCR level was associated with higher rates of inpatient mortality (odds ratio 1.29, p <0.001), hospital readmission within 30-days (odds ratio 1.25, p <0.001) and longer hospital length of stay (hazard ratio 1.25, p <0.001). Despite this, higher UCR was associated with lower rates of admission to ICU (odds ratio 0.84, p 0.016).
Conclusions: Elevated UCR is a strong predictor of poor clinical outcomes in CKD inpatients. Further studies are required to understand the physiological basis for this relationship and to determine whether interventions to prevent the accumulation of urea in CKD improve outcomes in this population.
Elizabeth is a Medical Intern at St Vincent’s Hospital in Melbourne with a keen interest in nephrology. She graduated from the Doctor of Medicine at The University of Melbourne in 2019 after completing a Bachelor of Biomedicine in 2015.