AUBF Lecture: Lesson 2 - Introduction of Urinalysis (Part 4) (unfinished)

specimen preservation

it involves using chemical preservatives or storage techniques to prevent degradation of analytes when immediate testing isn’t possible.

refrigeration, chemical preservatives

what are the 2 Methods of Preserving Urine Specimens?

2-8C

optimal temperature for refrigeration of specimen

refrigeration

most common method for preservation

bacterial growth, chemical changes

refrigeration slows down what?

precipitation of crystals, rewarmed

refrigeration may cause? and what must be done before testing?

Boric Acid

preserves bacteria for culture but can interfere with pH testing

Formalin

preserves cellular elements but not for chemical testing

Thymol

preserves glucose and sediment but may cause false positives for proteins

Toluene

forms an oily layer to prevent exposure to air and does not mix with urine

Sodium Fluoride

inhibits glycolysis and good for glucose testing

Use proper container and label correctly, Refrigerate if delay is expected, Mix specimen before testing (if refrigerated), Match handling to required test

What are the 4 do’s of best practices?

Don't leave specimen at room temp for >2 hours, Don't use incorrect preservatives, Don't expose to light unnecessarily, Don't freeze unless advised

What are the 4 don’ts of best practices?

oxidation or concentration of solutes

urine color darkens because of?

bacterial growth, precipitation of solutes

urine clarity becomes cloudy because of?

breakdown of urea to ammonia by bacteria

urine odor becomes ammonia-like because of?

urea-splitting bacteria produce ammonia

urine pH increases because of?

bacterial metabolism

urine glucose decreases because of?

volatilization and bacterial metabolism

urine ketones decreases because of?

light exposure and oxidation

urine bilirubin decreases because of?

oxidation to urobilin

urine urobilinogen decreases because of?

bacterial conversion of nitrate to nitrite

urine nitrite increases because of?

cell lysis in dilute/alkaline urine

urine RBC/WBC/Casts decreases because of?

proliferation without refrigeration

urine bacteria increases because of?

specimen integrity, preservation methods

what should be maintained and used appropriately to ensure that urine test results truly reflect the patient's health status because they are critical?

random urine, first morning, midstream clean-catch, 24-hour urine, timed urine, catheterized specimen, suprapubic aspiration, pediatric collection bag

what are the 8 types of urine specimen?

random urine

collected at any time of the day and used for routine urinalysis

random urine

easy to collect but may vary in concentration

first morning

collected immediately after waking up and used for pregnancy testing and microscopic exam

most concentrated; prefered