Details can found in the following section of the Bacterial Culture test.
  U. Urine

Deliver all specimens to the laboratory as soon as possible after
collection.  Gram stains are automatically performed on fluids and 
exudates other than blood and urine.  Do not send sterile body fluids 
in plastic red top tubes.  These tubes contain a clot activator which 
may affect testing.  Therefore, tests may be unreliable.

Label transport tube with two patient identifiers, date and 
time of collection. Transport at room temperature unless otherwise 
specified.