Our specimen freezing question arose in response to an October 6 post from Anne-Marie Quinn, Janssen-Ortho, Canada. The responses had a degree of unanimity not often seen on Fritsma Factor! Here they are:
How do you freeze coagulation assay plasma samples?
1. Place in a -20°C (household) freezer: 10 (20%)
2. Place in a -70ºC (laboratory) freezer: 40 (78%)
3. Place in an acetone-dry ice bath: 0
4. Place in dry ice: 1 (2%)
I’ll use this summary to reiterate the risks of using acetone-dry ice or isopropanol-dry ice for flash freezing and to recommend, as most of our responders support, a -70°C freezer, or if more instant freezing is desired, a liquid nitrogen freezer. Household freezers are often adequate, provided they do not have an automatic defrost cycle, which allows specimens to thaw and refreeze.