Dear Gregg Watts
The unit of B12 measurement is ng/L rather than pmol/L
you have used in your e-mail. I must say, we do not
give exact results for high B12 beyond the linearity
range. For Bayer Immuno 1 we report these as >2000
ng/L. We commonly see such high results in people on
B12 therapy and patients with liver cell damage and
myeloproliferative disorders. As with any immunoassay,
interfering antibodies should be investigated. The
simplest way is to use PEG precipitation of
immunoglobulins and re-analyse the supernatant for
B12. A dramatic reduction in the result proves the
presence of interfering antibodies. Needless to say
that there is no clinical significance attached to a
high B12 level (>2000 ng/L), that is why we do not
bother to dilute the sample to get exact results
Regards
Mohammad Al-Jubouri
--- Greg Watts <[log in to unmask]> wrote:
> A question for the wisdom of the group.
>
> We have had a questionable Vitamin B12 result of
> 25,635 pmol/L (ref interval
> 173 - 840) on a 78 year old lady visiting her GP.
> The clinical notes were
> "previously low B12"
>
> The doctor says she is not on supplements,
> injections, nor, surprisingly any
> medications. she is not visiting any other doctors
> (as far as she is aware.)
> Close questioning of the patient also confirms no
> supplementation.
>
> The instrumentation used was the Abbott Axsym. It
> was also checked using the
> boil RIA method of BioRad. A fresh sample was
> referred to another practice
> who use the ACS 180 and also measured a high level.
> Subsequent testing has
> showed a positive intrinsic factor antibody (the
> measurement of which is
> unreliable at high B12 levels).
>
> Does anyone know of a possible explanation for this
> high result? Can
> intrinsic factor antibodies interfere with the
> porcine intrinsic factor
> based assays, or could something else be going on?
>
> I look forward in anticipation to your replies.
>
> Greg Watts
> Senior Biochemist
> Sydney Adventist Hospital
>
>
> CAUTION: This message may contain both confidential
> and privileged
> information intended only for the addressee named
> above. If you are not the
> intended recipient you are hereby notified that any
> dissemination,
> distribution or reproduction of this message is
> prohibited. If you have
> received this message in error please notify the
> sender immediately, then
> destroy the original message. Any views expressed
> in this message are
> solely those of the individual sender, except where
> the sender is
> specifically authorised by Sydney Adventist Hospital
> to state that they are
> the views of Sydney Adventist Hospital.
>
>
>
=====
Dr. M A Al-Jubouri
Consultant Chemical Pathologist
Whiston Hospital
Prescot
Merseyside L35 5DR
UK
__________________________________________________
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.
http://im.yahoo.com
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|