The type of urine specimen collected and the method of collection are determined by the test requested. The following are the five most common forms of urine specimens. Some body fluids can also be tested to see if they contain urine.
First Morning Urine Specimen
Overnight, the bladder represents all of the urine from the previous 6 to 8 hours. It is a more precise reflection of the patient’s 24-hour urine than a random spot urine sample. Second, by collecting the urine specimen as soon as possible after waking up, postural changes that can affect the urine can be prevented. Third, diurnal variations can have an effect on test results. The first morning specimen helps us to plan the timing of the testing. Finally, since the urine was stored in the bladder during the relative overnight fast, it is concentrated, and testing is more likely to detect positive results. This specimen is suitable for detecting substances such as proteins and nitrates, and it is often used to confirm an orthostatic proteinuria diagnosis.
Although the first morning urine specimen is often preferred, it is not the easiest to obtain. It is necessary to send the patient guidance and the collection container at least one day before the specimen is required. Furthermore, if the specimen is not going to be sent to the laboratory within 2 hours of collection, it must be stored.
Random Urine Specimen
Urine specimens are typically collected at random during the day, with no prior patient planning. Routine screening is usually conducted on a random specimen for ease and convenience. Where the substance to be analyzed does not have substantial diurnal variance and its normal concentration is sufficient to be detected in a small amount of urine, random testing is normally performed. Random urine is also the preferred specimen for illicit drug testing. This prevents patients from tampering with outcomes or modifying their actions in preparation for research.
Timed Urine Collection
Since substances such as hormones, proteins, and electrolytes are excreted in varying amounts throughout the course of a 24-hour period, as well as the influence of exercise, posture, hydration, and body metabolism on excretion rates, quantitative urine tests often necessitate timed collection. These time spans can vary from 2 to 24 hours. There are two kinds of timed sets. Urine specimens collected at a predetermined time are one type. For example, glucose is often measured two hours after a meal (postprandial), since that is when the urine is supposed to have the highest glucose content. After every meal, a 2-hour postprandial specimen can be obtained. Specimens obtained at a specific time of day are included in the second category. A specimen for urobilinogen analysis, for example, is best obtained between 2:00 pm and 4:00 pm, when bilinogen is most excreted. A preservative may be needed to ensure consistency during the collection process, depending on the material being measured and the type of collection. Furthermore, some foods and medications may need to be avoided during the collection process.
The patient is told to void and discard the first specimen in order to collect a timed specimen. This is recorded as the test’s start time. All subsequent urine is saved in a special jar for the specified time span. The patient voids and adds this urine to the specimen container at the end of the agreed time span, completing the collection process.
This method of collection is used to acquire and test fresh urine. The patient must first empty his or her bladder in order to obtain this specimen. The patient voids again shortly after. The freshest urine is used for testing in the second specimen of the double-voided specimen. It correctly records blood concentrations at that time.
Urine Specimen for Culture and Sensitivity
This specimen is collected for bacterial testing. The specimen should be collected as aseptically as possible in a sterile jar. To avoid contamination of the specimen by foreign species, the urinary meatus must be meticulously cleansed with an antiseptic preparation. A midstream collection technique can clear the urethral canal of contaminant bacteria. The specimen should be cultured within 1 hour of being collected.
Other Body Fluids
To determine whether a fluid is urine, blood urea nitrogen (BUN) and creatinine levels can be measured in it. This is a common procedure performed following pelvic surgery. Urine can resemble abdominal fluid serous drainage. If the BUN and creatinine concentrations in the fluid match those found in serum, the fluid is classified as serous drainage or ascites. If the concentration of BUN and creatinine in the fluid exceeds three times that of serum, the fluid is urine. This testing is also used in obstetrics to distinguish between amniotic fluid and urine.