To perform a 24 hour urine sample:
- You should collect every drop of urine during each 24-hour period. It does not matter how much or little urine is passed each time, as long as every drop is collected.
- Begin the urine collection in the morning after you wake up, after you have emptied your bladder for the first time.
- Urinate (empty the bladder) for the first time and flush it down the toilet. Note the exact time (eg, 6:15 AM). You will begin the urine collection at this time.
- Collect every drop of urine during the day and night in an empty collection bottle. Store the bottle at room temperature or in the refrigerator.
- If you need to have a bowel movement, any urine passed with the bowel movement should be collected. Try not to include feces with the urine collection. If feces does get mixed in, do not try to remove the feces from the urine collection bottle.
- Finish by collecting the first urine passed the next morning, adding it to the collection bottle. This should be within ten minutes before or after the time of the first morning void on the first day (which was flushed). In this example, you would try to void between 6:05 and 6:25 on the second day.
- Please note the exact time of the final collection, even if it is not the same time as when collection began on day one.
- Keep the container in a cool place or refrigerator during the collection period, then bring the sample back to the hospital as soon as collection is complete.
24 Hour Urine Catecholamine Collection:
Urine is collected into bottles with acid preservative as catecholamines deteriorate without a preservative.
Stress and vigorous exercise can affect the test results.
Avoid the following foods for three days before the test and whilst collecting the sample:
|Beta-blockers||Caffeine||Catecholamines eg decongestants||Chlorpromazine||Diazoxide|
|Labetolol*||Lithium||Metaclopromide||Methyldopa||Nicotonic acid / Nicotine|
|Nitroglycerin||Sodium nitroprusside||Sotolol||Theophylline||Tricyclic antidepressants|
*does not interfere with plasma catecholamine measurement. However, these should be measured supine and cannulated for 30 minutes; plasma catecholamines can be elevated by kidney failure, caffeine, nicotine, exercise and some drugs.
Your doctor may ask you to discontinue some medication as some drugs decrease urine catecholamine measurements:
|Clonidine||Disulfiram||Guanethidine + adrenergic blockers||Imipramine||MAO inhibitors|
**present in radiocontrast
Some medications have variable effects on urine catecholamine measurements:
|Levodopa||Tricyclic antidepressents||Calcium channel blockers||ACE inhibitors||Bromocriptine|
Urinary metanephrine measurement: False positive elevations in metanephrine levels can be the result of sympathomimetics (pseudoephedrine – commonly found in OTC cold medications), tricyclic antidepressants, phenoxybenzamine, calcium channel antagonists.
Selective alpha1-blockers (doxazosin, prazosin, terazosin), beta-blockers, ACE-I, angiotensin II receptor blockers, diuretics do not interfere with the testing of metanephrines.
The urine should be collected in acid bottles as for catecholamines.