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Stability of prothrombin and factor VII in freeze-dried plasma
  1. M. Brozović,
  2. L. J. Gurd,
  3. I. Robertson,
  4. D. R. Bangham
  1. Division of Biological Standards, National Institute for Medical Research, Mill Hill, London
  2. Statistical Services Section, National Institute for Medical Research, Mill Hill, London


    The stability of prothrombin and factor VII was studied using accelerated degradation tests in three preparations of freeze-dried pooled normal plasmas. In a previous report (Brozović, Gurd, Robertson, and Bangham, 1971) factor X was shown to be relatively unstable in these preparations of freeze-dried plasma: it was calculated that up to 8% of the original factor X activity would be lost after 10 years at −20°C, up to 54% at 4°C, and up to 90% at room temperature.

    The losses of factor VII activity were estimated to be negligible at −20°C, between 2 and 18% at 4°C, and between 20 and 70% of the original activity at 20°C, after 10 years of storage. Prothrombin was found to be less stable than factor VII: the expected loss in 10 years at −20°C may be up to 4%, at 4°C up to 30%, and at 20°C up to 83% of the initial activity. These findings indicate that in freeze-dried plasma prothrombin as well as factor X may be insufficiently stable for plasma to serve as long-term reference material for the standardization of the one-stage prothrombin time. Moreover, the loss of prothrombin and factor X in freeze-dried plasma stored at 4°C may be so high that when it is required to preserve these factors it may be necessary to store freeze-dried plasma at lower temperatures.

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