AUBF

• Urine specimen


  • Readily available and easily collected
  • Contains information about many of the body's major metabolic functions
• The reasons for performing urinalysis identified by CLSI include aiding in the diagnosis of disease, screening asymptomatic populations for undetected disorders, and monitoring the progress of disease and the effectiveness of therapy
• Urine formation


  Kidneys continuously form urine as an ultrafiltrate of plasma
• Urine composition


  Urine is normally 95% water and 5% solutes, with urea being the largest organic component and chloride being the largest inorganic component
• Urine may also contain hormones, vitamins, medications, and formed elements like cells, casts, crystals, mucus, and bacteria</b>
• Urine volume


  Depends on the amount of water that the kidneys excrete, which is influenced by factors like fluid intake, fluid loss, ADH secretion, and need to excrete dissolved solids
• Oliguria


  Decreased urine output, often due to dehydration
• Nocturia


  Increased nocturnal urine excretion
• Polyuria


  Increased daily urine volume, often associated with diabetes mellitus or diabetes insipidus
• Diabetes mellitus


  Causes polyuria due to increased glucose levels that the kidneys cannot reabsorb
• Diabetes insipidus


  Causes polyuria due to decreased ADH production or function, leading to decreased water reabsorption
• Urine specimen collection


  • Must be in clean, dry, leakproof containers
  • Containers should have a wide mouth and flat bottom
  • Sterile containers should be used for microbiological studies
• Urine specimen labeling


  • Must include patient name, ID, date/time of collection, and other required information
• Urine specimen rejection


  • Reasons include improper labeling, contamination, insufficient quantity, improper transport/preservation
• Urine specimen handling


  • Should be delivered to lab promptly and tested within 2 hours, or refrigerated/preserved if delayed
• Improper preservation can seriously affect the results of a routine urinalysis
• Changes in urine


  • Eased
  • Decreased
  • Decreased
  • Decreased
  • Increased
  • Decreased
  • Increased
  • Decreased
• These variations are discussed again under the individual test procedures
• Specimen Preservation


  The method of preservation used most routinely is refrigeration at 2°C to 8°C, which decreases bacterial growth and metabolism
• If the urine is to be cultured, it should be refrigerated during transit and kept refrigerated until cultured, up to 24 hours
• The specimen must return to room temperature before chemical testing by reagent strips
• Refrigeration also can cause precipitation of amorphous urate and phosphate crystals
• Ideal preservative properties


  • Bactericidal
  • Inhibit urease
  • Preserve formed elements in the sediment
  • Not interfere with chemical tests
• The ideal preservative does not exist
• A preservative that best suits the needs of the required analysis should be chosen
• Types of Specimens


  • Random
  • First morning
  • 24-hour (or timed)
  • Catheterized
  • Midstream clean-catch
  • Suprapubic aspiration
  • Three-glass collection
  • Four-glass collection
• Random specimen


  Specimen received most commonly because of its ease of collection and convenience for the patient
• First morning specimen


  Ideal screening specimen, also essential for preventing false-negative pregnancy tests and evaluating orthostatic proteinuria
• 24-hour (or timed) specimen


  Necessary for measuring the exact amount of a urine chemical instead of just reporting its presence or absence
• Many solutes exhibit diurnal variations such as catecholamines, 17-hydroxysteroids, and electrolytes in which the lowest concentration is in the early morning and the highest concentration occurs in the afternoon
• If the concentration of a particular substance remains constant, the specimen may be collected over a shorter period
• Care must be taken to keep the patient adequately hydrated during short collection periods
• To obtain an accurate timed specimen, the patient must begin and end the collection period with an empty bladder
• The concentration of a substance in a particular period must be calculated from the urine volume produced during that time
• On its arrival in the laboratory, a 24-hour specimen must be mixed thoroughly and the volume accurately measured and recorded
• If only an aliquot is needed for testing, the amount saved must be adequate to permit repeat or additional testing
• If a specimen is collected in two containers, the contents of the containers should be combined and thoroughly mixed before aliquoting
• Consideration must be given to the preservation of specimens collected over extended periods
• All specimens should be refrigerated or kept on ice during the collection period and may require addition of a chemical preservative
• The preservative chosen must be nontoxic to the patient and should not interfere with the tests to be performed