[Histonet] Repeat validation when IHC protocol changed?

[Kevin_Kurtz <@t> ssmhc.com]

Recently our IHC vendor sent a tech to help us out with some weak staining 
affecting multiple antibodies.  Several staining protocols were changed, 
including adjusting the incubation time and adding amplification.  The 
results were great in the slides that I was shown.

The tech said that revalidation was unnecessary, since the changes to the 
protocol were considered "minor".  However, I personally disagree, since 
we don't know how the change in the staining protocol could potentially 
affect staining of other tissues (especially tissues that would be 
expected to be negative). Before subjecting our lab to the cost and effort 
of revalidation, I'd like to get your opinion.

For new antibodies, I usually validate using 10 cases expected to be 
positive and 10 cases expected to be negative for the antibody in 
question. For revalidation, I was thinking of running 5 positive cases and 
5 negative cases.

Thanks for your input - 

Kevin Kurtz, M.D.
St. Mary's Hospital
Madison, Wisconsin

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