YNHH Laboratory Manual

Spot urines are random samples of urine collected at any time. Timed urines are urines collected carefully over a fixed time, usually 24 hours. (The use of a 24 hour period eliminates fluctuations due to diurnal variations in excretion of many components.) At the start of a timed collection, the patient should void and the urine should be discarded. Thus, urine formed before the beginning of the collection period is not included in the collection. Subsequent urine specimens are collected into an appropriate container including a final void at the end of the collection period.

Many timed urine collections require special preservatives or refrigeration during the collection to avoid degradation of the analyte over the prolonged collection period. Be sure to collect the urine with the appropriate preservative or an entire day's worth of effort may be invalidated. Appropriate containers for spot urine collections are available on the floors. Containers for timed collections requiring no preservative are to be ordered from the hospital storeroom by the patient care area. Containers with preservatives may be obtained from Clinical Chemistry. Some specimens are preserved with acid or alkali. Patients and medical staff should be reminded to avoid contact with these preservatives and to wash immediately with copious amounts of water should contact occur.

Updated: July-2008