Hello:
Do any clinical laboratories no longer require diet restrictions prior
to testing urine VMA (vanillyl mandelic acid), metanephrines or
catacholamines?
The latest edition of the Manual of Clinical Dietetics (6th edition,
Am. Dietetic Assoc / Dietitians of Canada, 2000) states that more recent
assay techniques do not require dietary restrictions for VMA testing.
This manual is used across North America by hospital dietitians to plan
diets for patients and I suspect that computer tracking of hospital
foods (and food restrictions) has prompted our dilemma. The new manual
contradicts our laboratory protocol that states vanilla, coffee,
bananas, chocolate, cocoa should be avoided for several days prior to
and during the collection period.
My quick medline search revealed a half dozen papers in the past decade
that usually found effects if these foods were consumed during the 24
hour urine collection period prior to testing urine.
I assumed that the VMA or metanephrines detected in the urine are
derived from the foods and that the most recent assay techniques will
continue to detect these food-derived compounds.
We are currently using extraction and HPLC with electrochemical
detection which I believe is the most recent and reliable method
available. I concede that this HPLC method will have fewer
interferences than historic colourometric methods, but I still suspect
that dietary restrictions are required.
I am working with a local clinical dietitian to resolve this issue and
we hope to gather an informal survey of lab practices.
My questions [to those that have read this far and are willing to fire
off a quick reply :) ]
Does your lab continue to request diet restrictions prior to testing for
urine VMA, metanephrine and catacholamines?
What is the time interval of the dietary restriction ? (1,2, 3,4 or more
days?)
Thanks and Season's greetings,
Andrew
-
Dr. Andrew W. Lyon
Dept. Pathology and Laboratory Medicine,Univ. Calgary.
Calgary, AB, Canada
|