Although AABB guidelines are silent as to how blood product temperatures should be measured, virtually all commercially available chemical indicators have been calibrated to trigger based on core temperature. Essentially what they do is implement a color change at a preset temperature above 10 ºC in order to “simulate core”. This approach is very rudimentary and makes a lot of assumptions about the conditions and environment around the blood product. In addition to this they are also susceptible to false positives, which may contribute to inappropriate wastage.
In Section 1(a) of this report¹ from the Advisory Committee on Blood Components core temperature is referred to as the requirement for storage conditions in the UK and Europe.
Nearly all the major manufacturers of chemical indicators for blood products claim to measure core temperature.