At a Glance
Why Get Tested?
When to Get Tested?
The Test Sample
What is being tested?
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 globulins, including immunoglobulins. 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 symptoms. 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).
How is the sample collected for testing?
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.