16 terms

urine preservatives

advantages: doesnt interfere with chemical tests
disadvantages: raises specific gravity by hydrometer, precipitates amorphous phosphates and urates
other info: prevents bacterial growth
advantages: preserves glucose and sediments well; good for formed elements
disadvantages: interferes with acid precipitation tets for protein, inhibits bacteria and yeast
boric acid
advantages:preserves protein and formed elements well; doesn't interfere with routine analyses other than pH
disadvantages: may precipitate crystals when used in large amounts
other info: keeps pH at about 6
formalin (formaldehyde)
advantages: excellent sediment preservative; good for formed elements
disadvantages: reducing agent, interfering with chemical tests for glucose, blood, leukocyte esterase, copper reduction
other info: rinse specimen container with formalin to preserve cells and casts
advantages: doesn't interfere with routine tests
disadvantages: floats on surface of specimens and clings to pipettes and testing materials
sodium fluoride
advantages: prevents glycolysis, good preservative for drug analyses (tests for glucose)
disadvantages: inhibits reagent strip tests for glucose, blood, and leukocytes
other info: may use sodium benzoate instead of fluoride for reagent strip testing
advantages: doesn't interfere with routine tests
disadvantages: causes an odor change
other info: use 1 drop per ounce of specimen
commercial preservative tablets
advantages: convenient when refrigeration is not possible, have controlled concentration to minimize interference
disadvantages: may contain 1+ preservatives include sodium fluoride
other info: check tablet composition to determine possible effects on desired tests
urine collection kits
advantages: contains collection cup, C&S preservative tube or UA tube
gray C&S tube
advantages: sample stable at room tep for 48 hrs; preserves bacteria
disadvantages: decreases pH; do not use if urine is below minimum full line
other info: preservative is boric acid and may not be used for UA
yellow pain UA tube
advantages: use on automated instruments
disadvantages: must refrigerate within 2 hours
other info: round or conical bottom
cherry red/yellow top tube
advantages: stable for 72 hours at RT; instrument-capable
disadvantages: bilirubin and urobilinogen may be decreased if specimen is exposed to light and left at RT
other info: preservative is sodium propionate; conical bottom
saccomanno fixative
advantages: preserves cellular elements
other info: used only for cytology studies
uses: bilirubin, urobilinogen
problems: destroys formed elements
uses: calcium, phosphorus, delta-aminolevulinic acid
problems: routine UA, destroys formed elements, bactericidal
sodium carbonate
uses: porphyrins, prophobilinogen, urobilinogen
problems: routine UA