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ACB-CLIN-CHEM-GEN  1999

ACB-CLIN-CHEM-GEN 1999

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Subject:

Catechoalmine reference Intervals?

From:

Bill Bartlett <[log in to unmask]>

Reply-To:

Bill Bartlett <[log in to unmask]>

Date:

Fri, 25 Jun 1999 16:00:10 +0100

Content-Type:

multipart/mixed

Parts/Attachments:

Parts/Attachments

text/plain (65 lines) , Pheagrph.ppt (65 lines)

We also are confronted from time to time with the borderleine elevated
catecholamine result using ASTED. Our reference intervals (0.95
interfractile) are based on a worse case scenario in that they were derived
from a general hospital and GP population following exclusion of patients
with proven phaeo and exclusion of outliers using appropriate statistical
techniques. The population would appear appropriate since it includes the
usual rag bag of patients with hypertension (treated and untreated), funny
turns and banana addicts. This is the type of population we screen in
general.

By the time that most patients are being investigated for the presence of
phaeo, the majority have usually become acquainted with the contents of the
British Pharmacopoeia and we now fortunately have a reasonable library of
chromatograms from subjects  taking a variety of cocktails. The operators of
the system are very quick to highlight elevated catecholamines, strange
peaks, shoulders etc. We find that the main comments that append reports
tend to be individualised, and are usually appended with a request for drug
information and a requirement for the requesting physician to contact the
lab to discuss the case. The chromatograms have a built in safety feature in
that they also show the free metadrenalines, and we are very suspicious if
the apparrently high noradrenaline output is not associated with a high
normetadrenaline peak (this can happen in phaeo however).

We find we can explain many of the non-phaeo related elevations in terms
badly timed urine collections, drug interferences and specimens collected at
inappropriate times (in CCU on the day the patient had MI for instance). We
routinely measure urine creatinines to catch some of the funny collections,
and also use plots of the sum of creatinine corrected 24h urinary free
noradrenaline and adrenaline outputs against creatinine corrected free
dopamine outputs in some cases (see attached PowerPoint Slide (95)).  We
have shown that there is a significant positive correlation between these
indices, and that patients with phaeochromocytoma show a positive deviation
from the regression line applying to the reference population. The positive
deviation  is lost post tumour resection. Furthermore, I have had cases in
which the urinary free catecholamine excretion has fallen within the
conventional population reference intervals, but demonstrated a positive
deviation from the line. This may have been due to a deficiency in the
collection.

I can now expect some flack from some individuals about the problems
generated when you start measuring dopamines, but we think there are some
good reasons to measure it. 

On another note, I recall giving a talk on this subject at one centre and
was accused of being agressive when I suggested to a speaker that his
observation that there group didn't miss any cases of phaeochromocytoma,
using only HMMA as a screening test, was fallacious. It has  to be accepted
that the biological systems that we investigate present us with a continuum
ranging from normality to abnormality. It would seem reasonable to assume
the more dynamic and responsive that is being investigated, the less
categorical in our interpretations and comments. The sympathetic nervous
system would appear to present us with one such system (ask Rover).

  <<Pheagrph.ppt>> 
Dr WA Bartlett
Consultant Clinical Scientist
Clinical Biochemistry
Birmingham Heartlands Hospital
Birmingham B9 5SS

Tel. No. 0121 766 6611 Ext 5461.
Mobile 0374 103338


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