Hello Dr O'Connor,

You have brought up a topic which is simple to resolve (see below):

> We often find slightly elevated urine adrenaline and noradrenaline in
> patients who are under investigation for pheochromocytoma but do not have
> this condition. Usually the drug history indicates that the patient is
> taking some medication that is known to cause mild elevations in the
> catecholamines.
> 
> Our reference ranges are based on normotensive patients (should they be as
> the majority of patients under investigation are hypertensive?)

In the majority of cases the population you are investigating are
hypertensives  not normotensives. Furthermore they are commonly
hypertensives *on treatment*. Hence your reference range *must* be
based on a treated hypertensive population. [No-one would consider
using children to define a normal (reference) pulse rate for adults].

Pedants may argue that a treated hypertensive group are not
"normal". However we are *not* interested in the physiological
effects of hypertension and its treatment. We are concerned with
diagnosing a lethal but curable cause of a common condition
(hypertension). Too many false positive results (as  occurs using a
normotensive control group) will discourage  clinicians from doing
the test, or even worse, ignore the genuine positive results.


> Our ref ranges are as follows ....

Our reference ranges, based on treated hypertensive are as follows:

Noradrenaline <1000 nmol/24h (unconjugated ["free"]).
Adrenaline      <200   nmol/24h (unconjugated ["free"]).
Normetadrenaline: <4000 nmol/24h ( conjugated plus unconjugated).
Metadrenaline:      <2000 nmol/24h ( conjugated plus unconjugated).
We suggest that you find your own reference range which may 
be method dependent.

> Our protocol is to collect *3, 24h collections on consecutive
> days. (is this the best approach) 

Why? I have not seen any evidence that excretion of catecholamine or
its metabolites fall into the "reference range" in known
phaeochromocytomas. If you ask for multiple samples, clinicians are
less likely to investigate potential 'phaeos'. We only request repeat
samples when the results are borderline or if symptoms persist and
the clinician demands it.

>We do not routinely
> perform the Pentolinium suppression test in those patients with
> mildly elevated catecholamines to distinguish normal patients as
> this is a potentially hazardous procedure and we would be doing
> rather a lot of them. Do many of you do this procedure, if so what
> are your decision making criteria?

I see no reason for this test. If the clinician is convinced that
the patient has a 'phaeo' in the face of repeated negative urine 
tests (normetadrenaline and metadrenaline are the first choice), I 
would recommend a CT scan and/or MIBG test, since no surgical 
action can be taken until the tumour is found. 

> Do any labs have 'canned' interpretative comments for
> catecholamines if so what are they?.

We have three interpretative comments.
1. "Phaeochromocytoma unless disproven". [This forces the 
clinician to proceed with the important search for the tumour].
2. "Borderline result. Please repeat in six months".
3. "Normal catecholamine and metabolite excretion".

All positive results are *phoned directly* to the clinician involved
with patient management. This is essential.

We do not claim that normal results exclude a phaeochromocytoma,
however we have not found any false negative results. 
From: Dr Cyril Weinkove             Tel: +44 (161)-787-4427
      Clinical Sciences Building    Fax: +44 (161)-787-4427
      Hope Hospital, Salford        Email: [log in to unmask]
      M6 8HD,  United Kingdom       Internet:[log in to unmask]
      Home Message and Fax Mail:  +44 (171)-681-2373     


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%