A spot/random urine is preferred, please see Protein Electrophoresis - Spot/Random Urine.
A 24 hour urine collection is acceptable however it is not the preferred specimen.
A creatinine excretion test is performed on 24 hour urine collections in order to confirm the adequacy of the collection.
In timed urine collections other than 24 hours, (+/- 2 hours), the 24 hour excretion cannot be calculated due to different day time and night time excretion patterns of various analytes.
