[Histonet] Endogenous biotin blocking

JMyers1 <@t> aol.com JMyers1 <@t> aol.com
Wed Sep 2 14:16:53 CDT 2009

The simple answer to the question of whether or not biotin blocking is 
required is ‘no’.  As you stated in your inquiry, blocking need only be 
performed when excessive nonspecific staining, attributable to endogenous biotin, 
is observed. 

For what its worth, I think that some folks believe biotin blocking is 
required because they've miscontrued information contained within the College of 
American Pathologists AP checklist, which states: “If the laboratory uses 
an avidin-biotin complex (ABC) detection system...is there a policy that 
addresses nonspecific false positive staining from endogenous biotin?"  As 
written, this question only implies that an assessment of false positive staining 
be performed.  Therefore, provided that the lab conducts the recommended 
assessment, documents their results within appropriate policies/procedures, 
and then incorporates biotin blocking steps where they're needed, it does not 
have to perform blocking at all times. 

I'd welcome additonal input if my understanding is incorrect. 
Joe Myers, M.S., CT(ASCP) 


Message: 9
Date: Tue, 1 Sep 2009 08:31:56 -0400
From: Sally Price <sprice2003 <@t> gmail.com>
Subject: [Histonet] Endogenous biotin blocking
To: histonet <@t> lists.utsouthwestern.edu

I recently had a discussion with one of my coworkers about the 
need/requirement for blocking of endoegnous biotin whenever an avidin-biotin detection 
system is used, and I was hoping that the IHC
experts on the histonet might be able to provide us with some feeback.  Its 
been my understanding that blocking is only necessary when one is certain 
that background staining is caused by endogenous biotin, but maybe I'm 
off-base here.  I look forward to eveyone's input.

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