Microalbumin and
Microalbumin/Creatinine Ratio

The microalbumin test is an early indicator of kidney failure. It measures the tiny amounts of albumin that the body begins to release into the urine several years before significant kidney damage becomes apparent. Albumin is a protein that is produced in the liver. It is present in high concentrations in the blood, but when the kidneys are functioning properly, virtually no albumin is allowed to leak through into the urine. If a person’s kidneys become damaged or diseased, however, they begin to lose their ability to filter proteins out of the urine. This is frequently seen in chronic diseases, such as diabetes and hypertension, with increasing amounts of protein in the urine reflecting increasing kidney failure.

Since the albumin molecule is small, it is one of the first proteins to be detected in the urine with kidney damage. Patients who have consistently detectible amounts of albumin in their urine (microalbuminuria) have an increased risk of developing progressive kidney failure and cardiovascular disease in the future. Microalbumin measurements can be obtained using urine collected over a 24-hour period, for a specified amount of time (e.g., 4 hours or overnight), or randomly (spot).

Creatinine, a byproduct of muscle metabolism, is normally excreted into the urine on a consistent basis. Its level in the urine is relatively stable. Since the concentration (or dilution) of urine varies throughout the day, this property of creatinine allows its measurement to be used as a corrective factor in random/spot urine samples. When a creatinine measurement is performed along with a random microalbumin, the result is the microalbumin/creatinine ratio (also called the albumin/creatinine ratio (ACR)), which the American Diabetes Association states is the preferred test for screening for microalbuminuria.

You will be asked to collect either a random sample of urine while you are at the doctor's office or laboratory, a timed urine sample (such as 4 hours or overnight), or you may be requested to collect a complete 24-hour urine sample. Your doctor or the laboratory will give you a container and instructions for properly collecting a timed or 24-hour urine sample.

No test preparation is needed.