From the Guidelines
The albumin/creatinine ratio (ACR) is a crucial test for assessing kidney function, and a normal ACR is less than 30 mg/g, with values above this indicating potential kidney damage or disease, as recommended by the National Kidney Foundation guidelines 1.
Key Points to Consider
- The ACR test is essential for monitoring patients with diabetes, hypertension, or other conditions that increase the risk of kidney disease.
- A random spot urine sample is typically sufficient for accurate results, although first-morning samples may be preferred in some cases.
- The test should be performed annually for at-risk patients, with more frequent monitoring if abnormalities are detected.
- Elevated ACR values warrant further investigation and possible referral to a nephrologist, especially with persistent elevations.
- The ratio is valuable because it accounts for urine concentration variations, making it more reliable than measuring albumin alone.
Interpretation of ACR Results
- A normal ACR is less than 30 mg/g.
- 30-300 mg/g indicates microalbuminuria (early kidney damage).
- Over 300 mg/g signifies macroalbuminuria (more advanced kidney disease).
- At very high levels of proteinuria (spot urine total protein to creatinine ratio 500 to 1,000 mg/g), measurement of total protein instead of albumin on a spot urine sample is acceptable, as stated by the National Kidney Foundation and the National Institute of Diabetes and Digestive and Kidney Diseases 1.
Clinical Implications
- Early detection of elevated ACR allows for interventions like optimizing blood pressure control, managing diabetes, and medication adjustments that can slow kidney disease progression.
- The ACR test is a key component of chronic kidney disease management, enabling healthcare providers to monitor disease progression and adjust treatment plans accordingly.
From the Research
Albumin/Creatinine Ratio
- The albumin/creatinine ratio (ACR) is a widely used marker for chronic kidney disease (CKD) screening, with a cutoff of 30 mg/g or 300 mg/g 2.
- Studies have compared the urine dipstick test with ACR for CKD screening, finding that the dipstick test has poor sensitivity and high false-discovery rates for ACR ≥30 mg/g detection 2.
- Calculated ACR from urine dipstick protein or protein-to-creatinine ratio (PCR) can be used for risk predictions when measured ACR is not available, with PCR-calculated ACR having superior performance to dipstick-calculated ACR 3.
Clinical Cut-offs for Albumin/Creatinine Ratio
- Defining clinical cut-offs for ACR is essential for CKD diagnosis and progression, with studies attempting to establish percentage change in urinary ACR that reflects changes in CKD status 4.
- ACR cutoffs of 30 mg/g or 300 mg/g are commonly used to define albuminuria, with higher levels indicating greater kidney damage [(2,5)].
Treatment and Management
- Angiotensin-converting enzyme inhibitors (ACEis) and angiotensin II receptor blockers (ARBs) are recommended for reducing kidney disease progression in patients with proteinuria, with guidelines suggesting titration to maximum tolerated dose [(5,6)].
- However, studies have found that submaximal ACEi/ARB dosing is common among patients with proteinuria, with only 29.8% of patients taking maximal doses 6.
- Factors associated with lower odds of maximal ACEi/ARB dosing include age, sex, ethnicity, and comorbidities, highlighting the need for optimized treatment strategies 6.