At a glance
Also known as
24 hour urine protein; urine total protein; urine protein to creatinine ratio
Why get tested?
To detect excessive protein escaping into the urine, to help evaluate and monitor kidney function, and to detect kidney damage
When to get tested?
As part of a routine check-up, as a follow-up to a previous positive urine protein test, or if you have a disorder or disease that frequently affects the kidney
A or ; occasionally a split 24-hour sample, with the night collection separated from the day collection
What is being tested?
The urine protein test measures the amount of protein being excreted in the urine. There are several different kinds of urine protein tests. A semi-quantitative protein ‘dipstick’ is frequently performed as part of a urinalysis
, generally on a . The quantity of protein in a may be measured and reported as the amount of protein excreted per 24 hours. Also, the amount of protein in a random urine sample may be measured and reported as the ratio of protein to creatinine.
Since saving all of the urine for a 24-hour period can be cumbersome for adults and difficult for infants and children, a random urine protein to creatinine ratio may sometimes be substituted for a 24-hour urine protein sample.
Albumin, a protein produced by the liver, makes up about 60% of the protein in the blood. The rest is a mixture of , including . Proteins usually are not found in the urine. The kidneys (two organs found in the back at the bottom of the rib cage) filter the blood, removing waste and excreting it out of the body in the form of urine. When the kidneys are functioning normally, they retain or reabsorb filtered protein molecules and return them to the blood. If the kidneys are damaged, they become less effective at filtering, and detectable amounts of protein begin to find their way into the urine. Often, it is the smaller albumin molecules that are detected first. If the damage continues, the amount of protein in the urine increases, and globulins may also begin to be lost.
Proteinuria (protein in the urine) is frequently seen in chronic diseases, such as diabetes and hypertension (high blood pressure), with increasing amounts of protein in the urine reflecting increasing kidney damage. With early kidney damage, the patient often has no . As damage progresses or if protein loss is severe, the patient may have symptoms such as oedema (swelling and fluid retention), shortness of breath, nausea and fatigue. Excess protein production, such as may be seen with multiple myeloma, can also lead to proteinuria.
The presence of albumin in the urine (albuminuria) has been shown to be a good indicator of kidney disease in patients with diabetes and with high blood pressure. Therefore, in some situations the doctor may test specifically for albumin, as opposed to total protein in the urine (see microalbuminuria UACR).
How is the sample collected for testing?
A is collected in a clean container. For a , all of the urine is collected for a 24-hour period. It is important that the sample be refrigerated during this time period. There should be no preservative in the container.