Problems Associated with a 24 Hour Urine Collection

 

General instructions:

(1) The container should protect urine from the light. It should be clean, dry and free of detergents and chemicals.

(2) The specimen container is usually kept refrigerated. A chemical preservative may be added depending on what is being measured.

(3) Collection starts after voiding and discarding a first morning urine. All urine passed during the next 24 hours is collected completely.

(4) The specimen should be delivered promptly to the laboratory.

Issue	Solution
undercollection	proper instructions to the collector, collection in a controlled environment
overcollection	proper instructions to the collector, collection in a controlled environment
bacterial overgrowth	refrigeration or addition of a preservative
change in pH	addition of concentrated acid
chemical stability of compound	addition of a stabilizer
collection container	a clean, single use leak-proof container should be provided by the laboratory
exposure to temperature extremes during hot weather	do not leave the urine in the sun or exposed to a hot environment; it may be necessary to transport the sample in a cooler
chemical be measured is light sensitive	urine container usually opaque, else wrap container with aluminum foil

 

The most common problem is undercollection, with the patient failing to capture all of the urine passed.

 

Conditions that may make a complete collection difficult:

(1) incontinence

(2) polyuria (may require more than 1 container)

(3) mental or physical disabilities

(4) significant social problems (drug or alcohol abuse, etc)

 

Overcollection may occur if the person includes the first morning urine when starting and stopping the collection, rather than discarding the first one.

 

Any additive to the urine must be concentrated so as not to dilute the sample yet still be effective. A chemical salt added to the solution should not include any chemical that will be assayed (for example, potassium or calcium).

 

Sometimes multiple collections may be necessary if a stabilizer for one analysis interferes with another.

 

If a problem arises in the collection then it is often better to start a new collection.