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Urinary metanephrines - Investigation protocol

Indication

Urinary metanephrines are the first line screen for phaeochromocytoma.

Preparation

Patients may eat and drink normally prior to test. Written instructions must be given to the patient prior to performing this test to ensure that both 24 hour collections are performed accurately. Two special 24 hour collection bottles containing acid preservative should be provided to the patient in advance. Caffeine and cigarettes should be avoided for four hours, and all over the counter medicines should be avoided for 48 hours before the test, as paracetamol can cross react with assays and cough medicines may contain sympathomimetics.

Procedure

Patients are informed to choose two convenient days to perform their urinary collections. The two days need not necessarily be consecutive.  

Patients need to be advised that the collection bottles contain a preservative and so should not pass urine directly into them.

Patients are advised to empty their bladder into the toilet normally on waking on the morning that they start a collection and note the time. From that time onwards, all urine passed that day should be collected into a plain collection bottle. All urine passed during that night should also be collected.

The patient should set an alarm if necessary to wake them by the same time the following morning. That morning, the patient should empty their bladder and collect this as the final sample into the same bottle as from the previous day. This means that they start and finish the collection with an empty bladder at the same time of day.

The test should then be repeated on a second day and both collections brought in together for analysis.

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