False negatives using monoclonalPLAP

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From:Dave Tacha <dtacha@ncal.verio.com> (by way of histonet)
To:histonet <histonet@magicnet.net>
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In Response to Alex Brown:

There is a great abstract from the IAP meeting comparing monoclonal a
to a  polyclonal PLAP.  The polyclonal marks 80%-90% of classic seminoma
the monoclonal only marked 30-40%.  The total percentage of all germ
tumors studied was 85% with the polyclonal versus 15% with the
However both mark 100% for placenta.  I would not recommend a monoclonal

PLAP for screening.  Dako recently replaced their polyclonal with a
monoclonal.  I've talked to other techs and they say it does not perform
good a the polyclonal. After seeing results from the IAP paper, I would
to see a paper comes out comparing this new antibody.  I feel the same
about a monoclonal AFP or synaptophysin verses a polyclonal AFP or
synaptophysin,  At present, I have never found a monoclonal AFP or
synaptophysin to out perform a good polyclonal.  These are broad
antibodies that stain many different kind of tumors, both well and
differentiated. AFP, synaptopysin, and PLAP polyclonal antibodies stain
broader range tumors versus monoclonals.  I am not willing to give up
performance record for monoclonal antibody that marks 50% less tumors.
will be even more blunt.  Do not use a monoclonal PLAP until you have
performed side by side tests!  You are already seeing false negatives in

your lab.

David Tacha HTL (ASCP)
Biocare Medical Laboratories

Alex Brown wrote:

> Hi All,
>           We've recently been having some trouble with our Placental
> Alkaline Phosphatase (Plap).  i.e. variable results. Some tumours we
> expected to be positive, have been negative although the control (
> normal placenta) has been strongly positive. In one case recently, a
> tumour in testes (well fixed), allthough the tumour cells were
> unexpectedly negative, there was positive staining in smooth muscle
> fibres.
>         We use Dako's Primary (M7191, Clone 8A9) at 1:50 for 30mins ,
> microwave/pressure cook, and use Biogenix's HRP Kit and DAB. Staining
> carried out on the Optimax II.
>         Anyone else had any similar problems with this ??????
>                 Regards
>                         Alex. Brown
>                         Crosshouse Hospital
>                         Kilmarnock, Scotland.

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