Table 7 Summary of key pre-analytical recommendations about freezing and thawing
From: Pre-analytical issues in the haemostasis laboratory: guidance for the clinical laboratories
Freezing and thawing | Do not perform PT, aPTT and factor VIII tests from frozen samples. |
Centrifuge samples that cannot be tested within 4 h and frozen the plasma aliquot. | |
Use rapid freezing technique (liquid nitrogen). | |
Store samples at −70 °C (or below) rather than −20 °C. | |
Plasma samples frozen at minus 20 °C remain stable for 2 weeks. | |
Plasma frozen at minus 80 °C remains stable for 6 – 18 months dependent on the parameter. | |
Do not re-freeze samples (but prepare a sufficient number of aliquots). | |
Thaw samples rapidly at 37 °C (to prevent denaturing fibrinogen) at least 5 min in a water bath at 37 °C and not at room temperature, on a bench or in a microwave oven. Test immediately. | |
After thawing, mix the sample gently to resuspend any cryoprecipitate. Do not vortex or shake. | |
Do not re-frozen samples. |