What is the Albumin Creatinine Ratio (ACR) Test?

The Albumin Creatinine Ratio (ACR) test measures the amount of albumin, a type of protein, in your urine in relation to creatinine, a waste product. This ratio helps assess how well your kidneys are functioning. Elevated levels of albumin in the urine can be an early sign of kidney damage, particularly before other kidney function markers become abnormal.

Why is the 24-Hour ACR Test Performed?

The 24-hour urine ACR test involves collecting all urine produced over a 24-hour period. It provides a more accurate measure than a spot urine test and is often used in the following scenarios:

1. Early Detection of Kidney Disease

• Elevated ACR is one of the earliest markers of kidney disease, even if blood tests like creatinine or eGFR are still within normal range.

2. Monitoring High-Risk Patients

• Individuals with diabetes or high blood pressure are at increased risk for kidney damage. The ACR test helps monitor their kidney health over time.

3. Confirming Abnormal Results

• If a spot urine test (random sample) shows a high ACR, the 24-hour collection may be ordered to confirm and quantify the protein loss more accurately.

What Does the 24-Hour Urine ACR Test Measure?

• Albumin: A protein that should be present in the urine only in small amounts. Excess levels may indicate kidney damage.
• Creatinine: A metabolic waste product, used as a reference to determine the concentration of albumin relative to urine dilution.

How is the 24-Hour Urine Sample Collected?

1. Start at a Specific Time
   Begin collecting urine at a specified time in the morning (after discarding the first sample).
2. Collect All Urine for 24 Hours
   Every drop of urine after the first morning void should be collected into the provided container for the next 24 hours.
3. Store the Sample Properly
   Urine should be stored in a cool environment, often in a refrigerator, as per lab instructions.
4. Return the Sample Promptly
   At the end of the 24-hour period, return the full container to the lab within the time frame advised.

Understanding the Results

• Normal ACR
  • Typically less than 10 mg/g (or 1 mg/mmol) in healthy young adults.
• Elevated ACR
  • A ratio above 30 mg/g (or 3 mg/mmol) may suggest:
    • Kidney disease
    • Urinary tract infections (UTIs)
    • Other underlying health conditions
• Interpretation
  Your doctor will interpret the results in the context of your overall health, other lab tests, and medical history. Do not interpret the results on your own, as several factors can influence the ACR.

Final Note

The ACR test is a simple but powerful tool to detect kidney problems early, especially in people at risk. Early diagnosis can lead to better management, helping to prevent further kidney damage.