RE: storing controls

This reply is similar to what I sent out to Cheryl George a few minutes
back although it has not reached the Histonet yet.

What are your thoughts abought storing a positive control block in
refrigerator for a month (presumably to retain its "antigenicity" and nice
staining) and then cutting it and using  it as a control for a test or
patient block that has been sitting at room temp for a month? Unless all
blocks are stored in refrigerator.


Still in Seattle

                    Marjorie A."         To:     'Michelle Peiffer' <>,         
                    .org>                cc:                                                  
                                         Subject:     RE: storing controls                    
                    09:29 AM                                                                  


I am not sure how long controls last, I have not done a scientific study as
I am sure some have. Through experience we have found that paraffin blocks,
even unsealed, seem to retain antigenicity for a very, very long time.
Years. As for cut control slides - for some antigens (HER2) cut sections
remain at room temperature for just a matter of days before the
starts to decline. Immuno control slides deteriorate faster if they have
been incubated or stored at room temperature. From my experience, I would
recommend that controls slides be cut, but not incubated, and stored in the
refrigerator under dry conditions. The expiration on these slides is up for
grabs, I would be interested in what others have to say. We go through our
breast marker controls very rapidly and all others have a 1 year expiration
after they are cut. However, we go through the controls in a matter of a

Good luck,

Marjorie Hagerty H.T. (ASCP) H.T.L., Q IHC
Supervisor, Anatomic Pathology
Eisenhower Medical Center
39-000 Bob Hope Drive
Rancho Mirage, CA 92270


-----Original Message-----
From: Michelle Peiffer []
Sent: Thursday, April 05, 2001 7:29 AM
Subject: storing controls

Thanks to all who responded about my IHC decreased staining post.

Several people have mentioned storage of the controls.  Some are purchased
slides, so obviously they are precut and they are stored in the
refrigerator.  But most are freshly cut from blocks which are stored at
room temperature.  I was under the impression most people store blocks at
room temperature, is this correct?  How long can controls last?  We just
started doing histology so our oldest blocks are only 6 months old.


Michelle Peiffer
Electron Microscope Facility for the Life Sciences
Penn State University Biotechnology Institute
001 South Frear Lab
University Park PA 16802

phone: 814-865-0212

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