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Effects of Freeze-Thaw Times on Screening Coagulation Tests and Factors VIII and IX Activities in Citrate-Anticoagulated Plasma at -20°C and -80°C by Guofang Feng, Ying Zhao, Jie Zhang, Limin Feng

Background: Accurate determination of screening coagulation tests and factors VIII and IX activities (FVIII:C and FIX:C) in fresh plasma is very important for diagnosing abnormalities in the intrinsic or extrinsic coagulation pathways and factor deficiencies. If thawed samples cannot be detected for all required items at the same time, or need to be re-tested or re-stored, the thawed samples need to be re-frozen. We planned to perform in-house validation studies on freeze-thawed samples for screening coagulation tests, FVIII:C and FIX:C.
Methods: Mean percent changes, numbers of samples with > 10% changes, and difference plots were evaluated to determine clinically relevant differences between results for fresh and freeze-thawed samples. The statistical significance of differences between repeated-measure multiple groups and baseline values were evaluated by repeated-measures analysis of variance.
Results: The acceptable freeze-thaw cycles for activated partial thromboplastin time, fibrinogen, prothrombin time/international normalized ratio, thrombin time, and FIX:C were three times at -20°C/-80°C, while the acceptable freeze-thaw cycles for FVIII:C were three times at -80°C and once at -20°C.
Conclusions: The freeze-thaw results on stabilities were affected by time and temperature, with lower temperature and fewer times associated with more stable activity.

DOI: 10.7754/Clin.Lab.2018.180309