From the Guidelines
UACR stands for Urine Albumin-to-Creatinine Ratio, a crucial laboratory test for detecting early kidney damage, particularly in patients with diabetes or hypertension. This test measures the amount of albumin (a protein) in the urine compared to creatinine, requiring only a random urine sample, which is more convenient than a 24-hour urine collection. According to the most recent guidelines 1, normal UACR values are generally 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). The ratio is calculated because creatinine excretion is relatively constant, allowing albumin to be normalized against it, which controls for variations in urine concentration. Key points to consider when interpreting UACR results include:
- High biological variability of >20% between measurements in urinary albumin excretion 1, which necessitates that two of three specimens of UACR collected within a 3- to 6-month period should be abnormal before considering a patient to have high or very high albuminuria.
- Factors that may elevate UACR independently of kidney damage, such as exercise within 24 h, infection, fever, congestive heart failure, marked hyperglycemia, menstruation, and marked hypertension 1.
- The importance of regular UACR monitoring, recommended at least annually for diabetic patients, and every 6 months if eGFR is <60 mL/min/1.73 m2 and/or albuminuria is >30 mg/g creatinine in a spot urine sample 1, to detect kidney disease early when interventions can be most effective.
From the Research
UACR Lab Test
- UACR stands for Urine Albumin-to-Creatinine Ratio, a lab test used to diagnose and monitor kidney disease, particularly diabetic nephropathy 2, 3, 4, 5, 6.
- The test measures the amount of albumin (a protein) in the urine and compares it to the amount of creatinine (a waste product) in the urine 2, 4.
- A high UACR indicates kidney damage or disease, while a low UACR suggests normal kidney function 3, 5.
Clinical Significance
- UACR is a useful marker for detecting diabetic nephropathy, a common complication of diabetes 3, 6.
- The test can also be used to monitor kidney function in patients with chronic kidney disease (CKD) 4, 5.
- Studies have shown that UACR is a reliable and accurate test for detecting kidney disease, with high correlation coefficients and low coefficients of variation 2, 4.
Measurement and Interpretation
- UACR can be measured using a spot urine sample, which is a convenient and non-invasive method 2, 6.
- The test results are typically reported as a ratio of albumin to creatinine in milligrams per gram (mg/g) or micrograms per millimole (μg/mmol) 4, 5.
- Interpretation of UACR results requires consideration of various factors, including the patient's medical history, kidney function, and presence of other diseases 3, 5.