Understanding urine tests
Most people have already had a urine sample taken at some point in their life. A urine sample is needed for a urine test, which is used for instance to check for a particular disease or to monitor its progress. Using a urine test strip can already give an indication of a urinary tract infection, for example. But urine tests are usually just one of several possible tests that can be done to diagnose or rule out diseases. Here we explain the different urine tests, what they can test, and what the results can mean.
What does the quality of the urine tell us?
That urine is eliminated, is very important for different bodily functions. On the one hand, it regulates the balance of water in the body. On the other, substances are released along with the urine that are produced during metabolism and are no longer needed by the body. These also include toxic substances, which may have been absorbed from food, or medicines. By examining urine, indications for diseases of the urinary system can be detected and it can also provide evidence of metabolic diseases like diabetes or liver disease.
The color, odor and amount of urine can already help to find out whether something is wrong. If someone passes very little and very dark urine, it may indicate that he or she has not had enough fluids – or that the kidneys no longer function properly. Cloudy or flaky urine can indicate a urinary tract infection. If the urine is reddish in color, blood in the urine may be the reason. To find out more, laboratory testing is needed.
There are 5 standard urine tests, for examining the different components of the urine. Two of them can also be done in the home; the other 3 are only possible at the lab.
How do you take a urine sample?
Because urine can easily be contaminated with bacteria, cells and other substances it is a good idea to clean the genital area with water before the test – but without soap. To get a good result and avoid contamination with external bacteria, “clean” midstream urine is used for a urine test: urine is considered to be midstream when the first portion of the urine stream is not used, and only the middle part of the urine is caught in a cup. If there is anything else to be careful about for your specific test your doctor will tell you.
Rapid urine test
What is a rapid urine test?
A rapid urine test is the quickest way of examining urine. A test strip that has small square color fields is dipped into the urine for a few seconds. After that you will have to wait a little for the result. Depending on the concentration of the particular substance, the fields on the test strip change color. Then the resulting color of the fields is compared with a color table. The color table is printed on the urine test package. It shows which colors indicate normal and deviating values.
In a rapid urine test, a test strip is dipped into the urine and then compared with the color fields on the packaging.
A rapid urine test is usually done as part of a routine examination – for example at a doctor’s office, at an antenatal visit, when being admitted to the hospital, or before surgery. The test is also used for acute symptoms like lower abdominal pain, stomach ache or back pain, frequent and painful urination, or blood in the urine. Some people who have diabetes mellitus use this test to check their sugar levels.
The rapid urine test can be done at a doctor’s office, in a hospital, or at home. The test strips are available without a prescription at the pharmacy or on the internet. These tests are intended to be done in consultation with a doctor, and not to be used for self-diagnosis.
What can be tested with a rapid urine test?
Many substances are usually found only in a certain amount, so a higher or lower concentration indicates a deviation from the norm. “Reference: negative” means that a substance is not normally found in urine. The following substances can be checked using a rapid urine test:
- pH value (shows the acidity of the urine, reference, depending on diet, is about 5 to 7, with 5 meaning that acidity is too high, and 7 that it is too low)
- Protein (reference: negative)
- Sugar (glucose, reference: negative)
- Nitrite (reference: negative)
- Ketone (a metabolic product, reference: negative)
- Bilirubin (breakdown product of hemoglobin, reference: negative)
- Urobilinogen (breakdown product of bilirubin, reference: negative)
- Red blood cells (erythrocytes, reference: negative)
- White blood cells (leukocytes, reference: negative)
What do the results tell us?
Whether the results are within the reference range or not can be determined using the package insert or the color chart on the package. The pH value, for example, can be used to find out whether there is an increased risk of developing urinary stones. This is the case for acidic values, meaning values below 5. A pH value over 7 can indicate a bacterial urinary tract infection. Other results can help find other problems:
- High protein levels can indicate an inflammation of the kidneys,
- Ketone and sugar in the urine are signs increased blood sugar
- Leukocytes and nitrite can indicate a bacterial infection.
If the results are abnormal you need to speak with a doctor. As is the case with all tests, urine tests do not always produce reliable results. For this reason, it might be a good idea to have a more detailed test done at the lab.
What is urinalysis?
Urinalysis can be part of a routine examination and is frequently performed upon admission to the hospital and before surgery. The test can also follow a preliminary rapid urine test that produced abnormal results, so that urinalysis can be used to check those results. Complete urinalysis is done in a laboratory. It is usually made up of 3 parts:
- Assessment of the color, clarity and concentration of the urine
- Examination of the chemical composition of the urine with a test strip
- Examination of the urine using a microscope to identify bacteria, cells and cell parts
Microscopic examination of the solid parts of urine: the picture shows red blood cells (above), white blood cells (middle) and a cast of clumped-together white blood cells (below).
Urinalysis is used to find the cause of or monitor urinary tract infections, bleeding in the urinary system, or kidney or liver disease. It can also be used for diabetes, some diseases of the blood and bladder stones.
What can be tested with urinalysis?
In addition to the substances that can be tested for in a rapid test, urinalysis can examine the urine for the following:
- Creatinine (breakdown product of muscle metabolism, can be used to check the kidney function)
- Bacteria (reference: negative)
- Urinary casts (cylindrical stuck-together structures that form in the renal tubules, reference: negative)
- Crystals (are found if there are high concentrations of certain substances in the urine, reference: negative)
- Epithelial cells (line the ureter, bladder and urethra)
What do the results tell us?
With the help of these values a laboratory can also use urinalysis to determine the following indications:
- Cholesterol crystals can be caused by high levels of cholesterol, for example.
- Urinary casts are usually an indication of kidney disease like an inflammation of the kidney or the renal pelvis.
Abnormal results can be discussed with a doctor and may be followed by more exact tests, for example a blood test.
What is a urine culture?
A urine culture tests whether the urine contains germs. A sample of midstream urine is put into a container in a laboratory. Then small plates that have a growth medium that the germs can grow on are immersed in the sample and the container is closed tightly. The urine culture is then placed in an incubator for 1 to 2 days. If there are bacteria or fungi in the urine, they can form colonies.
Round culture dish with bacteria or fungi taken from the urine. These become visible after 2 to 4 days in the incubator.
What can be tested with a urine culture?
What do the results tell us?
A urine culture is usually done to detect bacteria and fungi in urine when testing for a urinary tract infection. If bacteria are found during laboratory testing, then the type of antibiotic needed can usually be checked at the same time.
24-hour urine sample
What is a 24-hour urine sample?
In this test urine is collected over a period of 24 hours: The first urine sample taken after waking up is not used and the time is noted. Starting at this point, for the next 24 hours every single drop of urine is collected in a container. After the 24 hours are up, the bladder is emptied one last time and the urine is added to the amount already collected. You will get the container for the urine sample from your doctor. The container usually already has an additional substance in it for preventing bacteria from growing during the collection time. The urine should be stored in a refrigerator for the entire 24-hour period. Afterwards, the urine is tested in a laboratory.
What can be tested with a 24-hour urine sample?
A 24-hour urine sample tests how much of certain substances (for example, proteins, hormones, salts, metabolic products) the body secretes.
What do the results tell us?
The test results can tell us, for instance, about the amount of protein and creatinine in the urine. If too little of the metabolic product creatinine is being filtered out of the blood by the kidneys, this can be a sign that the kidneys are no longer functioning properly. A high level of protein, which is called proteinuria, can be caused by the following conditions, for example: heart failure, diabetes mellitus, inflammation of the renal pelvis, urinary tract infections, kidney disease or cancer of the kidneys.
Some disorders of the hormonal system produce an increased amount of hormones and their metabolic products in the urine. In order to detect these disorders, urine is often collected over a 24-hour period on several days and then tested.
What is a pregnancy test?
When a period is skipped, there are special tests used to show whether a woman is pregnant. But these tests cannot give 100-percent reliable results. Most tests can already check 8 to 10 days after a missing period whether a woman is pregnant. These tests are usually done like the rapid urine test with the first urine produced in the morning after getting up. Because this can vary from test to test, you should read the package insert. A pregnancy test can be bought in a pharmacy, drug store, department store or over the internet.
What can be checked with a pregnancy test?
A pregnant woman’s urine contains a special hormone, the human chorionic gonadotropin (hCG). It is produced in the placenta.
What do the results tell us?
A pregnancy test is the first step for many women to find out if they are pregnant. If the test is done too early, or the woman has taken certain medications or drunk a lot, the result can be affected. To be sure about diagnosing a pregnancy or ruling it out, it is necessary to consult a doctor.
Other urine tests
Drugs can also be detected in urine for a certain time after they are used. Cannabis can be detected, depending on the type of test used, up to several weeks after it has been taken: drugs like cocaine, ecstasy or heroin for up to 5 days. Different tests are also used in detecting drug use: rapid tests, which can help give police fast results in the field, and other tests, that need to be done in laboratories. Urine samples are also used when giving athletes drug tests to check whether someone has used banned performance-enhancing substances.
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