Urine for clinical laboratory investigation – basic rules and requirements for urine collection, storage and transportation to the laboratory. Sources of errors. Cerebrospinal fluid, body fluid punktats and stool - basic rules and requirements for urine collection, storage and transportation to the laboratory. Sources of errors.
Laboratory testing of urine generally falls under three categories: chemical, bacteriologic, and microscopic examination. There are also several kinds of collection for urine specimens: random, clean catch, timed, 24-hour and catheterized.
Random specimens: may be collected at any time, but a first-morning-voided aliquot is optimal for constituent concentration as it is usually the most concentrate. Random urine specimens should be collected in a chemically clean receptacle, either glass or plastic.
A clean-catch, midstream specimen: Most Preferred method. Begin urination, stop midstream, discard this first portion of urine, then collect the remaining urine in a sterile container. The vessel is tightly sealed, labelled with the patient's name and date of collection, and submitted for analysis.
Urine specimens for a 24-hour total volume collection: are most difficult to obtain and require patient cooperation. Incomplete collection is the most frequent problem. In some instances, too much sample is collected.
Storage of urine: To prevent growth of microbes, the specimen should be refrigerated promptly after collection and, when necessary, contain the indicated chemical preservative.
Cerebrospinal Fluid: Lumbar punctures (LPs) are performed to collect cerebrospinal fluid (CSF) for laboratory evaluation to establish a diagnosis of infection. The most common site for lumbar puncture is between the 3rd and 4th lumbar vertebrae, or between the 4th and the 5th lumbar vertebrae. CSF require emergency transport and analysis
Pleural Fluid, Pericardial Fluid, and Peritoneal Fluid: Thoracentesis is a surgical procedure to drain fluid from the thoracic cavity and is helpful in diagnosing inflammation or neoplastic disease in the lung or pleura. Pericardiocentesis and peritonocentesis refer to the collection of fluid from the pericardium and the peritoneal cavities, respectively. These cavities normally contain less than 50 mL of fluid. Specimens are obtained for chemical, microbiologic, and cytologic examination and transferred to collection tubes with appropriate additive
Transport: Specimens should be protected from direct exposure to light, which causes breakdown of certain analytes (e.g., bilirubin). For analysis of unstable constituents' specimens must be kept at 4°C immediately after collection and transported on ice. All laboratory specimens must be transported in a safe and convenient manner to prevent biohazard exposure or contamination of the specimen.