L1: URINE PRESERVATIVES

refrigeration

• no interference with chemical test

• prevents bacterial growth for 24 hours

• > raised specific gravity by hydrometer

• > precipitates amorphous phosphate and urates

thymol

• preserves glucose and sediments well

• > interferes with acid precipitation test for protein

boric acid

• preserves protein and formed elements

• noninterference with routine analysis other than pH

• > may precipitate crystals

formaldehyde

• excellent sediment preservative

• > interferes with chemical tests

toluene

• does not interfere with routine test

• > floats on urine surface

sodium fluoride

• prevents glycolysis

• good for drug analysis

• > inhibits reagent strip for glucose, blood, leukocyte

phenol

• no interference with routine tests

• > cause an odor change

commercial preservative tablets

• convenient when refrigeration is not possible

• > may contain one or more preservatives including sodium fluoride

urine collection kits

• contains collection cup

• c and s preservative tube

gray culture and sensitivity tube

• sample stable at room temperature for 48 hours

• preserves bacteria

• > decreases pH

yellow plain ua plus tube

• use on automated instruments

• > must refrigerate within 2 hours

cherry red/yellow top tube

• stable for 72 hours at room temperature

• instrument compatable

• > may decrease bilirubin and urobilinogen

saccomano fixative

• preserves cellular elements

• used for cytology studies