The Urine Test Guide
By Adam Reger, Tests.com Contributing Writer
A urine test analyzes an individual's urine. Because a urine test can indicate the presence of a number of diseases and conditions, a doctor may request a urine test as part of a routine health screening. A urine test may also be requested to determine pregnancy or to look for specific diseases, such as an infection of the urinary tract or kidneys. A doctor may request the test in order to track the progression of existing, chronic conditions such as diabetes or hypertension. Doctors also use urine tests to determine whether a patient has particular conditions such as kidney stones, inflammation of the kidney and muscle breakdown.
Urine tests are also sometimes administered as pre-employment drug tests for prospective employees.
How Urine Tests Work
Urine tests are generally administered in a healthcare or laboratory facility. The patient is given a sterile cup with which to collect the urine and shown into a lavatory. Early morning is generally considered to be the best time for urine collection, as the urine is most concentrated at that time.
The most common method of collection is called the clean catch or midstream urine collection. As the name suggests, this method involves allowing a small quantity of urine to flow out of the body, into the toilet, before holding out the cup to collect the sample. Only about 10 to 15 milliliters (or the equivalent of about four tablespoons) are required. Once this amount has been collected, the patient can replace the lid on the cup and return the sample to the health care or laboratory professional. In the case of a urine sample being given at home, the rule of thumb is that the sample should be delivered to the laboratory within one hour, or refrigerated if that is not possible.
A method of collection that is sometimes preferred is called double-voided collection. In this method, the patient urinates into the toilet without collecting it, then drinks a large glass of water. After 30 or 40 minutes, the patient gives a sample.
Urine Test Preparation
Prior to taking a urine test, the patient should avoid foods that color the urine, such as rhubarb, blackberries or beets. The patient's doctor may have specific advice, such as avoiding taking pills and supplements such as vitamin B, phenazopyridine (Pyridium), rifampin, and phenytoin (Dilantin), which can alter the color of the urine. Diuretics may also affect the quality of the urine.
Urine Test Results
Even before the urine sample is analyzed in a laboratory, it can be inspected visually for irregularities in appearance through a process called macroscopic urinalysis. For example, whereas normal urine is light yellow and transparent, cloudiness of the urine may suggest infection, dehydration, liver disease or blood in the urine; foamy urine indicates abnormal amounts of protein. The odor of the urine may also be analyzed: diabetes and starvation produce a sweet odor, while the presence of the e. coli bacteria may produce a bad odor.
A more thorough, but still quick, analysis is urine dipstick chemical analysis. This process uses a urine dipstick, a plastic strip covered with different-colored squares, each of which tests for a different component. After the dipstick is submerged in the urine sample, a laboratory technician or doctor can interpret the color changes of the squares to make an analysis. While the dipstick test has the advantages of being quick and cost-effective, it is thought to be less accurate than other tests since it can indicate irregularities but does not give a clear indication of how abnormal an individual's urine is.
The most thorough method of urine testing is microscopic urinalysis, or the study of the patient's urine through a microscope. This method of testing primarily looks for cells, bacteria, and crystals in the urine that can assist the doctor or lab technician in making a clinical assessment. Prior to analyzing the urine through a microscope, the lab technician will use a centrifuge to separate the liquid and solid parts of the urine. The solid part is then mixed with a small amount of liquid urine, and one drop is viewed through the microscope, first at low power and then at a higher power of the microscope.
Once urine test results are received, a doctor will interpret them in conjunction with a patient's other symptoms to make a diagnosis.
Planning on taking a urine test? Check out our Urine Test Directory.
Source: MedicineNet, medicinenet.com