dxy

The current guidelines (United Kingdom Blood Transfusion Services/National Institute for Biological Standards and Control, 2002) specify cryoprecipitate as ‘the cryoglobulin fraction of plasma obtained by thawing a single donation of FFP at 4 ± 2C; while ‘plasma, cryoprecipitate depleted’ (also known as ‘cryo-poor plasma’ or ‘cryosupernatant’) is ‘the supernatant plasma removed during the preparation of cryoprecipitate’. The precipitable cryoproteins are rich in FVIII, von Willebrand factor (VWF), FXIII, fibronectin and fibrinogen. After centrifugation, the cryoproteins are separated and resuspended in a reduced volume of plasma. Although the guidelines set no limit, most UK blood centres prepare cryoprecipitate in volumes of 20–40 ml. The cryoprecipitate specification requires that 75% of packs contain at least 140 mg of fibrinogen and 70 IU/ml of FVIII. It should therefore be noted that multiple packs of cryoprecipitate may provide less fibrinogen than two or three packs of FFP (depending on volumes of original component in each final pool).

Cryosupernatant plasma is depleted in FVIII and fibrinogen; but whereas the FVIII concentration may only be about 0Æ11 IU/ml proportionately less fibrinogen may be removed, leaving up to 70% remaining (Shehata et al, 2001). Cryosupernatant is deficient in high molecular weight (HMW) multimers of VWF, but contains VWF metalloproteinase.

3. Pathogen-reduced plasmas (PRFFP and PRP)

The UK Departments of Health have recommended that the FFP given to neonates and children born after 1 January 1996 should be obtained from an area free of BSE and subjected to pathogen-reduction procedures. Older patients whose previous exposure to other blood components is limited but who are likely to be exposed to many doses of FFP (such as plasma exchange for TTP) may also benefit if PRP is used, but it may be difficult to anticipate the likely scale of need. In order to reduce the risk of the recipient developing TRALI (see Section 9.3), the donors should preferably be male.

3.1. Methods of producing PRP: quality monitoring

There are two methods of inactivating pathogens in plasma for clinical use: treatment with methylene blue and light (MBFFP); and solvent detergent (SDFFP). The key features of these products are shown in Table III (modified from Williamson, 2001).

3.1.1. MBFFP. The United Kingdom Blood Transfusion
Services/National Institute for Biological Standards and Control (2002) specify MBFFP in which the pathogenreducing methylene blue is not removed (so the product will contain about 1Æ0 lmol of methylene blue) and also ‘FFP, methylene blue-treated and removed’ which contains no more than 0Æ30 lmol of methylene blue. The latter option is usually preferred. MBFFP derived from UK donors of group AB is available for children and neonates.

At the time of writing (December 2003) supplies of the different types of MBFFP varied geographically within the UK, and no non-UK plasma was yet available. Although FFP from male donors may reduce the risk of inducing TRALI, such preparations are not universally available. MBFFP from AB male donors is sometimes available in packs containing 50–75 ml. During 2004, donor plasma from parts of the world believed to be of low BSE incidence, and pathogen reduced by the MB process, will be supplied for children born after 1996 when it becomes available.

3.1.2. SDFFP. 
Earlier materials, such as the ‘Octaplas’ used by Solheim et al (2000), were prepared from pools of 400 to 1200 donations. More recent batches are made from up to 2500 pooled units of thawed FFP. SDFFP lacks HMW-VWF and has a reduced activity of protein S. ‘Octaplas’ is licensed and available on prescription. The product must be ABO group compatible with the patient.

3.1.3. Pathogen-reduced cryoprecipitate and cryosupernatant currently these are not generally available in the UK.

3.1.4. Quality monitoring. 
The current guidelines (United Kingdom Blood Transfusion Services/National Institute for Biological Standards and Control, 2002) specify that, in addition to the features described in Section 2.1, MBFFP has at least 0Æ50 IU/ml of FVIII. This is in contrast with standard FFP (0Æ70 IU/ml FVIII).