Urine Preservatives

Question 1

Refrigeration

Answer 1

Advantage: Does not interfere with
chemical tests
Disadvantage: Precipitates amorphous
phosphates and urates

Question 2

Acids (boric acid,
HCL, acetic acid,
tartaric acid)

Answer 2

Advantages: Prevents bacterial growth
and metabolism
Disadvantages: Interferes with analysis of
drugs and hormones

Question 3

Formalin (formaldehyde)

Answer 3

Advantage: Excellent sediment
preservative
Disadvantage: Acts as a reducing agent,
interfering with chemical
tests for glucose, blood,
leukocyte esterase, and
copper reduction

Question 4

Sodium fluoride

Answer 4

Advantage: Good preservative for drug
analyses
Disadvantages: Inhibits reagent strip tests
for glucose, blood, and
leukocytes

Question 5

Commercial preservative
tablets

Answer 5

Advantage: Convenient when refrigeration not possible
Have controlled concentration
to minimize interference
Disadvantage: Check tablet composition to
determine possible effects
on desired tests

Question 6

Urine Collection Kits
(Becton, Dickinson,
Rutherford, NJ)

Answer 6

Advantage: Contains collection cup,
transfer straw, culture and
sensitivity (C&S) preservative tube, or UA tub

Question 7

Light gray and gray
C&S tube

Answer 7

Advantage: Specimen stable at room
temperature (RT) for
48 hours; prevents
bacterial growth and
metabolism
Disadvantage: Do not use if urine is below
minimum fill line

Question 8

Yellow UA Plus tube

Answer 8

Advantage: Use on automated
instruments
Disadvantage: Must refrigerate within
2 hours

Question 9

Cherry red/yellow
Preservative Plus tube

Answer 9

Advantage: Specimen stable for
72 hours at RT;
instrument-compatible
Disadvantage: Must be filled to minimum
fill line
Bilirubin and urobilinogen
may be decreased if specimen is exposed to light
and left at RT