Protein/Creatinine Ratio (Spot Urine)

Specimen Required

Urine (Random/Spot)

Fasting Required

Purpose of the Test

To detect excessive protein escaping into the urine, to help evaluate and monitor kidney function, and to detect kidney damage

When this test is required

A dipstick urine protein test is measured whenever a urinalysis is performed. This may be done as part of a routine check-up, a pregnancy check-up, when a urinary tract infection is suspected, as part of a hospital admission, or whenever the doctor wants to evaluate kidney function. It may also be done when a previous dipstick has been positive for protein to see if the protein excretion persists.The laboratory random or 24-hour urine protein test may be requested as a follow-up test when the dipstick test shows that there is a large quantity of protein present in the urine and/or when protein is shown to be persistently present. Since the dipstick primarily measures albumin, the doctor may request a laboratory urine protein test even when there is little protein detected on the dipstick if they suspect that there may be proteins other than albumin being released.When a doctor is diagnosing the cause of proteinuria they also may request a urine electrophoresis test to determine exactly which proteins are being excreted and in what quantities. A serum electrophoresis also may be used to look at the proteins in the blood, especially if abnormal protein production is suspected. Other blood tests, such as a urea and creatinine, may be used to evaluate kidney function and a albumin and/or total protein may be used to look at the proteins in the blood.A protein to creatinine ratio may be requested on a random urine sample when a child shows evidence of significant and persistent protein in their urine on a dipstick urine test. It may also be requested when a patient has known kidney disease and/or damage and the doctor wants to monitor kidney function over time. A dipstick urine protein and/or a protein to creatinine ratio on a random urine sample may be used as a screen for kidney involvement when a patient is receiving treatment that may potentially affect kidney function.

What the Test Detects

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 random urine sample. The quantity of protein in a 24-hour urine sample may be measured and reported as the amount of protein excreted per 24 hours. Also, the amount of protein in a random…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 random urine sample. The quantity of protein in a 24-hour urine sample 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. Creatinine, a by-product of muscle metabolism, is normally excreted into the urine at a constant rate. When a creatinine measurement is performed with a random urine protein test, the resulting protein/creatinine ratio can be used instead of the 24-hour urine protein test. 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). See MoreSee Less

Preparation for the Test

None

Sample Requirements

A random urine sample is collected in a clean container. For a 24-hour urine collection, 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.

Additional Notes

The different methods of detecting protein in the urine vary in performance. For example, a positive dipstick protein may be elevated due to other sources of protein, such as blood, semen, or vaginal secretions in the urine. Since it measures primarily albumin, the dipstick occasionally may be normal when significant quantities of other proteins are present in the urine. A 24-hour urine sample gives the protein excretion rate over 24 hours. It will be accurate only if all of the urine is collected. A random laboratory protein to creatinine ratio measurement is now considered the preferred means of assessing proteinuria and is recommended in UK National Service Frameworks (NSF) and in guidelines for the identification, management and referral of Chronic Kidney Disease (CKD).

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