One of the main reasons for invalid results of urine tests is improper specimen collection and maintenance. Therefore, the nurse must know how the specimens are collected and how to instruct clients on specimen collection. The various types of specimens are discussed here.
Random specimens are urine samples that are collected at any time of day in clean containers. Usually 15 to 60 mL of urine is sufficient for tests performed on random samples. Random samples are used for routine screening tests to detect obvious abnormalities. The client is instructed to void directly into the urine container or to void in some other type of clean container, after which the sample is transferred to another type of laboratory container. If the sample is collected by the client at home, it must be transported to the laboratory within 2 hours or test results may be inaccurate.
First morning specimens are collected upon arising in the morning, when urine is most concentrated. Such samples are ideal for screening purposes, because substances may be detectable in them that are not found in more dilute samples. In addition to routine screening tests, first morning samples are desirable for pregnancy tests and tests for orthostatic proteinuria.
Double-voided specimens are used when testing urine for sugar and acetone. The purpose of this approach is to ensure that the urine tested is fresh so that it serves as a valid indicator of current blood glucose and ketone levels. The client is instructed to empty the bladder and, if possible, to drink a glass of water. Approximately 30 minutes later, the client voids again. The second sample is then tested. Some individuals advocate testing the first sample as well, in case the client cannot void a second time. The validity of results on the first sample may be questionable, however. The double-voided specimen is particularly critical for the first urine sample of the day because urine that has accumulated in the bladder overnight is not a valid indicator of current status.
Clean-Catch Midstream Specimens 
Clean-catch midstream specimens are used to avoid contamination of the sample with urethral cells, microorganisms, and mucus. The procedure is as follows: The client is provided with a clean-catch kit containing a sterile specimen container and materials for cleansing the meatus. The male client should cleanse the urinary meatus with the agent provided (or with soap and water), void a few milliliters of urine into the toilet or urinal, and then void directly into the specimen container. Women should cleanse the labia minora and meatal orifice carefully, working from front to back, and then manually keep the labia separated while voiding a few milliliters into the toilet or bedpan. With the labia still separated, the client should then void directly into the collection container. If a woman is menstruating or has a heavy vaginal discharge, she should insert a clean vaginal tampon before beginning the cleansing process. Care must be taken by all clients to avoid touching the inside of the urine container and lid.
Clean-catch midstream urine specimens are used primarily for microbiologic and cytologic analysis of urine. Some individuals also advocate using this method for specimens for routine urinalysis, especially in women, because the sample is less likely to be contaminated with substances that alter results of routine screening tests.
Urine specimens can be obtained from one-time "straight" catheterizations or from indwelling Foley catheters. "Straight" catheterization is indicated when the client is unable to void for a random or a clean-catch specimen without excessively contaminating the sample. It is also used for samples for microbiologic and cytologic studies.
Indwelling catheters may be placed for a variety of reasons. In some cases, they may be inserted when serial urine specimens are needed at exact time intervals. In other cases, the catheter is already in place and must be used for urine sampling.
When obtaining a sample from an indwelling catheter, be sure that the drainage tube is empty; then clamp the tube distal to the specimen collection port. The sample is obtained with a needle (25- to 21-gauge) and a 3- to 5-mL (larger if a greater amount is needed) syringe after the tubing has been clamped for approximately 15 minutes. The specimen port is cleansed with an antiseptic swab (e.g., alcohol sponge) and the sample is aspirated. The sample is then placed in a sterile container or rubber-stoppered test tube and sent promptly to the laboratory. Bedside screening tests (e.g., for glucose and ketones) may be performed by instilling the sample directly from the syringe to the reagent strip. Care must be taken to ensure that the catheter is unclamped after the sample is obtained.
Twenty-Four-Hour (Timed) Specimens
Twenty-four-hour specimens allow quantification of substances in urine. Methods of preserving the accumulating sample vary among laboratories and, therefore, the laboratory should be consulted for advice regarding the use of a preservative or the need for refrigeration, or both. It is critical that all urine excreted during the 24-hour period be collected.
When a 24-hour specimen is required, it is desirable to begin in the morning, usually sometime between 6 and 8 AM. First the client voids and discards the specimen. The collection begins when the discard sample is obtained. All urine voided thereafter is collected. The next day, at the same time the specimen collection began, the client is instructed to void again. This final voiding is added to the sample, and the collection ends. The dates and times of specimen collection should be noted on the laboratory slip. In the hospital setting, it is helpful if a reminder to collect all urine is posted in or near the client's bathroom so that neither the client nor the hospital personnel inadvertently discard any portion of the specimen. The client should be instructed not to place toilet paper in the specimen container (devices that fit into toilet seats are often used). Individuals who use a bedpan should be instructed not to void into a pan containing feces.
Sometimes it is necessary to insert a Foley catheter for 24-hour urine collections, especially if the client is unable to participate in specimen collection. Other times, a Foley catheter may already be in place. When a 24-hour urine collection is to be obtained via an indwelling catheter, the collection should begin by changing the tubing and drainage bag so that a clean, fresh system is in use. If a preservative is required, it can be obtained from the laboratory and placed directly into the drainage bag. Others advocate using a container with preservative and emptying the drainage bag contents into it at frequent intervals (e.g., every 2 hours). If refrigeration of the specimen is necessary, the drainage bag is placed in a basin filled with ice. The ice supply must be renewed frequently to ensure that the specimen is properly chilled. If the urine must be protected from light, the drainage bag may be covered with dark plastic or with aluminum foil. If the drainage tubing is positioned correctly for continuous drainage, it need not be covered.
When the collection is completed, the sample should be transported promptly to the laboratory. Some urine tests require 2-hour samples. A 2-hour sample is collected in the same manner as a 24-hour sample, with the exact starting and stopping times noted.
Suprapubic aspiration involves inserting a needle directly into the bladder to obtain a urine sample. Because the bladder is normally sterile, this method allows collection of samples that are free of extraneous contamination. In this procedure, the skin over the suprapubic area is cleansed with antiseptic and draped with sterile drapes. A local anesthetic may then be injected. The needle is inserted and the sample is removed, after which a sterile dressing is applied. The site is observed for inflammation and abnormal drainage. Suprapubic aspiration may be used for samples for microbiologic and cytologic analysis. It may also be used to obtain samples in infants and young children.
Pediatric urine collections can be performed for random, first voided, clean-catch, or timed specimens. For infants, this procedure involves the attachment of a plastic collection device to the male penis or to the female genitalia to collect the urine. A female infant is placed in a supine position with the hips rotated and abducted and the knees flexed. The perineal area is cleansed and dried, and the collection device is taped to the perineum at the point between the anus and the vagina. The adhesive edges of the device toward the front and over the pubic area are sealed to prevent leakage of urine. A male infant is placed in supine position, and the penis and scrotum are cleansed and dried. The device is applied over the penis and scrotum and the edges are sealed against the perineum to prevent leakage of urine. A diaper is placed over the collection device. The device is removed after the specimen is obtained to prevent loosening of a moist bag. The urine is placed in a clean container, labeled correctly, and sent to the laboratory. A clean-catch specimen is collected using the same appliances applied after cleansing with soap or an antiseptic pad and then with sterile water. The specimen should be tested immediately for accurate results, because the number of bacteria can double every 20 to 30 minutes. If the infant has not voided within 45 minutes, the bag is removed and the cleansing and application are repeated. A 24-hour specimen collection requires a special collection bag that contains a collection tube attached to a container device that can be emptied periodically. Testing with Tes-Tape can be accomplished by placing a cotton ball in the diaper to collect the urine and placing the tape on the wet cotton ball. The wet diaper can also be used for this type of testing. Urine specimens are obtained from toilet-trained children in the same manner as for adults. It is helpful to follow the child's usual urinary pattern when collecting the specimen. A potty chair or bedpan placed on the toilet and terminology familiar to the child should be used ("tinkle," "potty," and so on). A parent can assist and often has more success in collecting a specimen than does a nurse.
- Random Specimens
- First Morning Specimens
- Double-Voided Specimens
- Clean-Catch Midstream Specimens
- Catheterized Specimens
- Twenty-Four-Hour (Timed) Specimens
- Suprapubic Aspiration
- Pediatric Samples