A urine test is any medical test performed on a urine specimen. The analysis of urine is a valuable diagnostic tool because its composition reflects the functioning of many body systems, particularly the kidneys and urinary system, and specimens are easy to obtain.[1] Common urine tests include the routine urinalysis, which examines the physical, chemical, and microscopic properties of the urine; urine drug screening; and urine pregnancy testing.
Example of a container used for collecting 24-hour urine samples. This particular container is free of trace metals to allow for accurate measurement of these substances in urine.
The techniques used to collect urine specimens vary based on the desired test. A random urine, meaning a specimen that is collected at any time, can be used for many tests. However, a sample collected during the first urination of the morning (first morning specimen) is preferred for tests like urinalysis and pregnancy screening because it is typically more concentrated, making the test more sensitive.[1][9] Because the concentration of many substances in the urine varies throughout the day, some tests require timed urine collections, in which the patient collects all of their urine into a container for a given period of time (commonly 24 hours). A small amount of the specimen is then removed for testing. Timed collections are commonly used to measure creatinine, urea, urine protein, hormones and electrolytes.[1][10]
If urine is needed for microbiological culture, it is important that the sample is not contaminated. In this case, the proper collection procedure involves cleaning the genital area, beginning to urinate into the toilet, and then filling the specimen container before completing the urination into the toilet. This is called a "midstream clean catch" collection.[1] Research has shown many women are unsure of how to take a midstream sample or why it is needed.[11][12]
If the subject is not able to urinate voluntarily, samples can be obtained using a urinary catheter or by inserting a needle through the abdomen and into the bladder (suprapubic aspiration).[3] In infants and young children, urine can be collected into a bag attached to the genital region, but this is associated with a high risk of contamination.[1]
^ abQueremel Milani DA, Jialal I (8 May 2022). "Urinalysis". StatPearls. PMID32491617. Archived from the original on 5 April 2022. Retrieved 13 July 2022.
^Wu X (March 2010). "Urinalysis: a review of methods and procedures". Critical Care Nursing Clinics of North America. 22 (1): 121–128. doi:10.1016/j.ccell.2009.10.012. PMID20193886.
