From the Guidelines
Urine albumin-to-creatinine ratio (uACR) is the preferred method for assessing kidney function and detecting early kidney disease, rather than urine microalbumin testing, due to its ability to account for urine concentration variations and provide a more reliable assessment. This recommendation is based on the most recent and highest quality study, which emphasizes the importance of uACR in monitoring kidney function in patients with diabetes, hypertension, or known kidney disease 1. The study suggests that annual testing for albuminuria should begin in pubertal or post-pubertal individuals 5 years after diagnosis of type 1 diabetes and at the time of diagnosis of type 2 diabetes, regardless of treatment.
Key Points
- uACR measures the ratio of albumin to creatinine in a spot urine sample, providing a standardized assessment of kidney function
- The normal uACR is less than 30 mg/g, with 30-300 mg/g indicating moderately increased albuminuria and values above 300 mg/g representing severely increased albuminuria
- uACR testing is particularly important for monitoring kidney function in patients with diabetes, hypertension, or known kidney disease
- A single spot urine sample for uACR is convenient and sufficient for screening, though confirmation of abnormal results with repeat testing is recommended
Clinical Implications
The use of uACR has significant implications for clinical practice, as it allows for early detection and monitoring of kidney disease. By detecting increased urinary albumin, which represents glomerular damage, healthcare providers can identify patients at risk of kidney disease before changes in glomerular filtration rate become apparent. This enables timely interventions to slow disease progression and improve patient outcomes. As stated in the guidelines, timed collection for urine albumin should be done only in research settings and should not be used to guide clinical practice 1.
Evidence Summary
The evidence from the study published in 2023 1 supports the use of uACR as the preferred method for assessing kidney function and detecting early kidney disease. The study provides recommendations for annual testing for albuminuria and emphasizes the importance of using morning spot urine albumin-to-creatinine ratio (uACR) for measurement. The guidelines also recommend that first morning void urine sample should be used for measurement of albumin-to-creatinine ratio, and if first morning void sample is difficult to obtain, all urine collections should be at the same time of day 1.
From the Research
Comparison of uACR and Urine Microalbumin
- uACR (urine albumin-to-creatinine ratio) and urine microalbumin are both used to detect kidney damage, particularly in patients with type 2 diabetes 2, 3.
- uACR is considered a sensitive and early indicator of kidney damage, and its use is recommended for routine assessment of CKD stage and monitoring of kidney health 2.
- Urine microalbumin, also known as microalbuminuria, is an important clinical marker for the early detection of kidney damage in patients with type 2 diabetes, and its presence is associated with an increased risk of end-stage renal disease and cardiovascular disease 3, 4.
Diagnostic Accuracy and Variability
- The diagnostic accuracy of uACR and urine microalbumin can be affected by various factors, including hypertension, diabetes duration, and glycemic control 3, 5.
- uACR has been shown to demonstrate a high degree of within-individual variability, which can make it challenging to interpret changes in albuminuria over time 5.
- Multiple urine collections for uACR may be necessary to improve the accuracy of diagnosis and monitoring of kidney disease, but may not be required for initial diagnosis 5.
Clinical Implications and Recommendations
- Clinical guidelines recommend annual testing for chronic kidney disease using both eGFR and uACR in patients with type 2 diabetes 6.
- However, testing rates for uACR are often suboptimal and highly variable across different healthcare organizations and clinical practice sites 6.
- Increasing uACR testing rates can lead to improved detection of kidney disease and potentially better outcomes for patients with type 2 diabetes 6.