[Histonet] AFB= bad ctrl for Fite, Negative controls, decloaker,egfr

[Richard Cartun]

Dear John:

I was interested in your comments regarding EGFR testing.  I have been
using Zymed's mAb (clone 31G7) for years and it almost always gives more
immunoreactivity than the mAb in DakoCytomation's EGFR kit.  For the
determination of patient eligibility for anti-EGFR therapy, we report
the result for the Dako test, but we always run the Zymed mAb in
parallel, and sometimes use it to help us determine if a patient's tumor
is truly positive (or negative).

Richard Cartun

>>> "JOHN COLEMAN" <JPCOLEMA <@t> sentara.com> 05/07/04 02:48PM >>>
Using an AFB control for a Fite stain is a dangerous game! It is quite
possible for the control to look positive when the capsule of the
bacteria in question on the test slide is present and dissolved and the
slide therefore looks negative!

For Negative controls, in addition to matching all the rest of the
protocol like you already are doing, you must at least also apply the
same diluent used for the primary antibodies since letting the slide dry
out will in most cases alter the stainability of the slide if there were
an issue of false positivity gotten from the secondary reagents,
retrieval or other ancillary procedures or reagents.

Biocare's decloaker is basically a fine tuned lab grade pressure
cooker- we use neither. We tried the pressure cooker offered by
Cellmarque, and it saved us no time, and did not significantly improve
retrieval.What antibody are you having trouble with? I could tell you
what we do if it's one we use. 

I tested 6  EGFRs on 45 breast cancer and 30 colon cancers looking for
a percentage that matched that of Dako's kit and I have to say that the
kit's clone is the best I've found. The other clones have a 5-10 %
staining of all cases and The Dako kit had a yield closer to 50%, which
is what the research for the drug claims. We bit the bullet ( price tag)
and now order the kit.
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