From the Guidelines
A normal urine albumin-to-creatinine ratio with normal urine creatinine and albumin levels is a strong indicator of healthy kidney function, suggesting no evidence of kidney damage or disease, as supported by the most recent guidelines 1. This finding is crucial because it implies that the kidneys are functioning properly, filtering blood without allowing abnormal amounts of protein (albumin) to leak into the urine. The albumin/creatinine ratio is particularly valuable because it accounts for variations in urine concentration, providing a more reliable assessment than measuring albumin alone.
Key Points to Consider
- Normal values are typically less than 30 mg/g, with values between 30-300 mg/g indicating microalbuminuria (early kidney damage) and values above 300 mg/g suggesting macroalbuminuria (more significant kidney damage) 1.
- For patients with risk factors such as diabetes, hypertension, or family history of kidney disease, regular monitoring of this ratio is recommended even when values are normal, typically annually for diabetic patients and as clinically indicated for others 1.
- The test is important because kidney damage often progresses silently, and detecting abnormalities early allows for interventions that can slow or prevent progression to chronic kidney disease.
Clinical Implications
- Annual testing for albuminuria is recommended for adults with diabetes using morning spot urine albumin-to-creatinine ratio (uACR) 1.
- If estimated glomerular filtration rate is <60 mL/min/1.73 m2 and/or albuminuria is >30 mg/g creatinine in a spot urine sample, the uACR should be repeated every 6 months to assess change among people with diabetes and hypertension 1.
- Referral to a nephrologist is recommended in cases of uncertainty about the etiology of kidney disease, difficult management issues, and rapidly progressing kidney disease 1.
From the Research
Significance of Normal Urine Albumin-to-Creatinine Ratio
- A normal urine albumin-to-creatinine ratio (UACR) with normal urine creatinine and albumin levels is significant in assessing kidney health, particularly in patients with type 2 diabetes mellitus 2, 3.
- UACR is a sensitive and early indicator of kidney damage, and its measurement is crucial in accurately assessing chronic kidney disease (CKD) stage and monitoring kidney health 2.
- A UACR <30 mg/g is considered normal, but even a mildly elevated UACR level within the normal range can be associated with an increased risk of CKD progression 3.
Association with CKD Complications
- UACR and protein-creatinine ratio (PCR) are both important markers of kidney damage and are used for prognosis in persons with CKD 4.
- Higher UACR and PCR levels are associated with lower serum hemoglobin, bicarbonate, and albumin levels, as well as higher parathyroid hormone, phosphorus, and potassium levels 4.
- The associations of UACR and PCR with common CKD complications are similar, suggesting that routine measurement of PCR may provide similar information as UACR in managing immediate complications of CKD 4.
Comparison with Other Screening Methods
- The urine dipstick test is a widely used screening tool for albuminuria, but it has poor sensitivity and high false-discovery rates for UACR ≥30 mg/g detection compared to UACR assessments 5.
- UACR assessments appear beneficial for a more accurate prediction of worse quality of life in CKD screening, and may be preferred over urine dipstick tests for CKD risk categorization 5.
Variability and Monitoring
- UACR demonstrates a high degree of within-individual variability among individuals with type 2 diabetes, which can present a challenge to interpreting changes in albuminuria 6.
- Multiple urine collections for UACR may improve the capacity to monitor changes over time in clinical and research settings, but may not be necessary for the diagnosis of albuminuria 6.