Graham
We have been running catecholamines on overnight urine samples and reporting
results as ratios to creatinine for over 6 years. It was Bob Peaston's work
at the Freeman Hospital, Newcastle that persuaded us to go this way, which
was published in J Clin Endocrinol Metab 1996; 81:1378-84. In addition to
being easier for the patient to collect, sleep urine samples also tend to
reduce the effects of stress and exercise on catecholamine production in
'non-phaeo' patients.
Our method uses a cation exchange trace enrichment cartridge to clean the
sample, which is then separated isocratically using reverse phase ion pair
chromatography with electrochemical detection. The overnight reference
ranges for an adult hypertensive population we use are:
Noradrenaline <48 nmol/mmol creatinine
Adrenaline <10 nmol/mmol creatinine
Dopamine <300 nmol/mmol creatinine
We have not encountered any significant problems and on the occasions when
our results are either borderline or clearly elevated on several samples,
the 24 hr urine levels have generally given relatively similar results.
Regards,
Roy
Roy Fisher
Consultant Biochemist
Royal Cornwall Hospital
Truro
-----Original Message-----
From: Graham Jones [mailto:[log in to unmask]]
Sent: Thursday, April 18, 2002 23:33
To: [log in to unmask]
Subject: Re: Urine catecholamines
Regarding urine catecholamines:
I would like to follow up a comment by Jeffrey Barron about catecholamines
being expressed as a ratio to creatinine. I realise that Jeffrey only
mentioned this as a trigger for further investigation, but if it useful it
would be a great boon to our patients. However I have my doubts...
With a 24 hour (or other timed) collection we are measuring the amount of
adrenaline (or whatever) produced over the time period. For example a 1 cm
secreting lesion producing the same amount of secretory products would give
the same increase in a big or a small person. Creatinine correction does
two things, it reduces the within-person variation due to changes in
hydration, but also corrects for body muscle mass. Thus the same lesion in
a person with a small muscle mass would produce a higher response than the
same lesion in a larger person when corrected for creatinine.
I know of a case where a "lesion", subsequently shown to be normal adrenal
was recently removed from a very small person, largely in response to
grossley elevated cats:creat ratio (plus severe hypertension plus lump on
the adrenals). The timed levels were borderline elevated on one of three
occasions I think.
I would be very inetrested if anyone has evidence supporting the use of
spot samples for creatinine, or interpretration of catecholamine:creatinine
ratios in timed collections (leaving aside the use of creatinine to help
determine adequacy of collection.
Regards,
Graham
Graham Jones
Staff Specialist in Chemical Pathology
St Vincent's Hospital, Sydney
Victoria St, Darlinghurst, 2010
NSW, Australia
Ph: (02) 8382-2170 Fax (02) 8382-2489
[log in to unmask]
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