Dear all,
We, along with a number of others, feel that a functional assay (eg
urinary methylmalonate) is more use than measuring B12 on it's own. As
such, we have an assay specifically for this purpose and have already
begun a service.
Regards, Roy.
Dr R Talbot.
Clinical Biochemist,
Department of Clinical Chemistry,
Sheffield Children's Hospital,
Western Bank,
Sheffield.
S10 2TH.
(0114) 2717479.
>>> "John M. Land" <[log in to unmask]> 4/9/07 17:36:15 >>>
Dear Peter,
Your last point is on the money! Practically every reference range for
B12 determined by way of a functional test be it tHcy or
methylmalonate
has a bottom reference interval which is far to low. This is well
documented in the literature but the Haematologists who first set up
B12
ranges based upon MCV as far as I can see appear to be unaware of
this.
We have many patients who have a peripheral neuropathy that has
responded, with electrophysiologically documented improvement, to B12
who otherwise one would consider to have 'normal' B12s. The other
question is should one actually be measuring B12 or better
holotranscobalamin. I think the latter but imagine the effort changing
the textbooks let alone attitudes.
Great that you have raised this.
JML
Dr John M. Land
Clinical Director Biochemical Medicine
UCLH NHS Foundation Trust
Neurometabolic Unit Box 105
National Hospital
Queen Square
London WC1N 3BG
44-(0)20-7829-8768
-----Original Message-----
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of Sharpe, Peter
Sent: 04 September 2007 16:58
To: [log in to unmask]
Subject: Reference range for Roche vitamin B12
Dear All,
If anyone would be happy to share their reference range for Roche
vitamin B12, I would be much obliged. We are currently using 140 - 640
pg/ml, derived from both in-house data and consultation with other
Roche
users. However, Roche are recommending 191-663 pg/ml in their kit
insert
(data derived from a German population), although they do state that
differences exist with respect to population and dietary status.
If we were to move to the Roche recommended values, 11% of our total
requests for B12 would be "deficient" as opposed to 4.3% using our
current lower cut-off value 140 pg/ml. We have always had a population
with lower than average B12 levels and this was also seen when we used
Abbott Architect in the past. I worry about this lower value in the
reference range as those who fall below it are usually treated with
B12
injections (perhaps unnecessarily). On the other context, we could be
missing B12 deficiency as a cause of neurological features etc.
Any advice (and your reference range) would be much appreciated.
Best wishes
Peter
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