Microalbuminuria (Spot Urine)

What is microalbuminuria?

Albumin is the most abundant protein in the blood, and healthy kidneys largely prevent it from passing into the urine. When damage begins in the kidneys' filtering units, albumin can appear in the urine in amounts too small to be detected by a standard urinalysis. This is called microalbuminuria; current guidelines also refer to it as moderately increased albuminuria. This early sign of kidney damage often appears before any changes show up in blood tests.

In the spot urine test, both albumin and creatinine are measured in a single urine sample, and the result is reported as the albumin/creatinine ratio. Because creatinine reflects how concentrated or dilute the urine is, this ratio provides a reliable assessment without the need for a 24-hour urine collection. The unit of the result expresses the amount of albumin in milligrams per gram of creatinine. The measurement is performed in the laboratory using sensitive immunological methods.

When is a microalbuminuria test ordered?

Microalbuminuria usually causes no symptoms, so regular screening is important for people at risk. Kidney involvement detected early can be slowed with measures such as better control of blood sugar and blood pressure. The test also gives an indication of the risk of heart and vascular disease.

• Type 1 or type 2 diabetes
• High blood pressure (hypertension)
• Chronic kidney disease or a family history of kidney disease
• Heart and vascular disease or high cardiovascular risk
• Monitoring the effect of kidney-protective treatment

How should you prepare for a microalbuminuria test?

You do not need to fast for the microalbuminuria test. For a reliable result, the first morning urine is preferred, although a sample collected later in the day can also be evaluated. You should avoid strenuous exercise on the day before the test, because intense physical activity, fever, a urinary tract infection and menstrual bleeding can temporarily raise the albumin level. If any of these apply, it is advisable to postpone the test for a few days or to mention it.

The sample is collected from the middle part of the urine stream into a sterile container after the genital area has been cleaned. Passing the first and last parts into the toilet reduces contamination of the sample with cells from outside. If you would like to have the test at home, a sterile container is delivered to you; you collect the sample yourself, and the nurse picks up the container and takes it to the laboratory. You do not need to stop your blood pressure or diabetes medicines for the test, but it is helpful to mention the medicines you take.

What does a microalbuminuria result mean?

A result below the laboratory's reference limit shows that there is no significant loss of albumin in the urine. A value above the reference limit suggests that the kidneys' filtering system may be affected at an early stage. Because albumin excretion can vary from day to day, a single high result is not considered enough for a diagnosis; usually two out of three measurements repeated within three to six months need to be high.

Persistently high levels can point to kidney damage related to diabetes or high blood pressure, as well as an increased risk of heart and vascular disease. A very high value may indicate that kidney disease is more advanced and calls for further investigation. Reference values may vary by laboratory, age and sex; this laboratory's reference range is shown on this page. The result should be evaluated by a doctor together with blood creatinine, the estimated glomerular filtration rate, your symptoms and other findings.