The Urinary Albumin-Creatinine Ratio (UACR) is a clinical test used to quantify the amount of albumin being excreted in the urine. It provides insight into kidney function, and particularly, the kidney’s filtering capability. Here’s a breakdown:
- Albumin: This is a protein that is present in the blood. Normally, only trace amounts of albumin are found in urine because the kidneys are efficient at retaining proteins. However, if the kidneys are damaged or not functioning properly, they may allow more albumin to escape into the urine.
- Creatinine: This is a waste product that forms when creatine, which is found in muscles, breaks down. The kidneys filter creatinine from the blood to be excreted in the urine. The amount of creatinine production is relatively constant, depending on muscle mass, making it a useful marker to assess renal function.
- The Ratio: By looking at the ratio of albumin to creatinine in a urine sample clinicians can gauge the degree of albuminuria while accounting for variations in urine concentration.
Clinical Significance:
- A higher UACR value indicates greater amounts of albumin in the urine, which can be a sign of kidney damage or disease.
- It’s a particularly useful test for people with diabetes or hypertension, as these conditions can lead to kidney damage, and an increased UACR can be an early sign of this damage.
- The categorization is:
- Normal: <2.5 (male) <3.5 (female) mg/mmol
- Microalbuminuria: 2.5-25 (male) 3.5-35 (female) mg/mmol
- Macroalbuminuria: >25 (male) >35 (female) mg/mmol
Regularly monitoring UACR in individuals, especially those with risk factors for kidney disease (such as diabetes or hypertension), is vital for the early detection and management of kidney diseases.
The gold standard is 24 hour urine albumin:
- Normal: <30mg
- Microalbuminuria: 30-300mg/day
- Macroalbuminuria: > 300mg/day