[Histonet] Frozen IF Specimen Storage: Is -80 C really necessary; will -20 C work?

[DAVID HENDERSON]

We routinely store our frozen IF specimens (renal and skin biopsies) embedded in OCT and sealed in plastic bags for at least 4 yrs in a -80C freezer. Cases that are positively diagnosed by the pathologist, are used as positive controls for subsequent IF staining. In practice, most positive controls are used within 1-2 years of their original storage.

Our -80C freezer has died, and we are temporarily storing in a different -80C freezer in another building on campus. My supervisor asked me to research whether or not a -20C freezer will suffice for our storage needs, or must we anti up for the much more costly -80C replacement or repair. 

I would appreciate receiving suggestions backed by experience, or educated thoughts about the advisability of -20C storage of specimens for future IF staining.

Thanks,
David Henderson, HTL
RML, Tulsa, OK