From the Guidelines
An elevated Urine Albumin to Creatinine Ratio (UACR) indicates kidney damage or disease, with a value of ≥30 mg/g Cr defined as high urinary albumin excretion 1.
Key Points
- UACR is a continuous measurement, and differences within the normal and abnormal ranges are associated with renal and cardiovascular outcomes 1.
- Factors affecting UACR include preanalytical factors, intraindividual variability, preanalytical storage conditions, non-renal causes of variability in creatinine excretion, and analytical factors 1.
- Transient increases in UACR can occur with short-term hyperglycemia, exercise, urine tract infections, sustained blood pressure elevation, heart failure, fever, and hyperlipidemia 1.
- Albuminuria is defined as UACR ≥30 mg/g and is an early indicator of diabetic kidney disease in type 1 diabetes and a marker for development of diabetic kidney disease in type 2 diabetes 1.
Clinical Implications
- UACR should be measured in patients with diabetes or those at risk for kidney disease, and two of three specimens collected within a 3- to 6-month period should be abnormal before considering a patient to have high or very high albuminuria 1.
- eGFR should be calculated from serum creatinine using a validated formula, such as the CKD-EPI equation, and an eGFR persistently <60 mL/min/1.73 m2** in concert with a **urine albumin value of >30 mg/g creatinine is considered abnormal 1.
- First morning urine samples are preferred for measuring UACR due to relatively low intra-individual variability and correlation with 24-hour protein excretion 1.
From the Research
Elevated Urine Albumin to Creatinine Ratio (UACR) Indications
- An elevated UACR is associated with an increased risk of all-cause and cardiovascular mortality, even within the normal range (<30 mg/g) 2, 3.
- Higher UACR levels are linked to a higher risk of cardiovascular mortality in patients with coronary artery disease, with or without type 2 diabetes mellitus 4.
- UACR variability is high in individuals with type 2 diabetes, and multiple urine collections may be necessary to accurately monitor changes in albuminuria over time 5.
- A UACR cutoff point of >10 mg/g can significantly predict the cumulative incidence and progression of chronic kidney disease (CKD) in patients with type 2 diabetes mellitus 6.
Association with Mortality and CKD Progression
- Elevated UACR is associated with increased risk of all-cause and cardiovascular mortality, with a near-linear relationship between UACR and mortality risk 2, 3.
- The association between UACR and mortality risk is more pronounced in adults with poor cardiovascular health status 3.
- Higher UACR levels are linked to an increased risk of CKD progression in patients with type 2 diabetes mellitus, even at levels considered within the normal range (<30 mg/g) 6.
Clinical Implications
- Early detection of albuminuria and careful evaluation of UACR, even within the normal range, are crucial to reduce mortality risk and prevent CKD progression 2, 6.
- Multiple urine collections for UACR may improve the capacity to monitor changes in albuminuria over time, but may not be necessary for the diagnosis of albuminuria 5.