Re: False negatives using monoclonal PLAP

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From:James Ito <> (by way of histonet)
To:histonet <>
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I asked our immuno specialist about this. She remembers DAKO admitting at an
immuno quality control meeting that they were having problems with PLAP. We
don't do many, but have had some success with the DAKO mono using the DAKO
CSA kit to amplify the otherwise rather weak result.

Jim Ito,
Pathology Department,
Royal Hospital for Sick Children

-----Original Message-----
From: Dave Tacha <>
To: <>
Date: 02 December 1998 15:21
Subject: False negatives using monoclonalPLAP

>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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