Cryoprecipitate prepared from plasma treated with methylene blue plus light: increasing the fibrinogen concentration

summary. When cryoprecipitate is prepared from plasma which has been treated with methylene blue plus light (MB) for the purpose of virus inactivation, clottable fibrinogen content is 40% lower compared with units prepared from untreated plasma. Initial studies showed that when frozen MB plasma units were removed to +2 to +6 °C for 4 h and then returned to −40 °C prior to cryoprecipitation, fibrinogen recoveries increased from 24 to 42%. Although fibrinogen yield improved when plasma units were stored at +2 to +6 °C for varying lengths of time, FVIII levels decreased with increasing time. Conditioning for 8 h was studied in more detail. Groups of two plasma units were mixed together, divided into two equal units, frozen/thawed and treated with MB. One of each pair was stored continually at −40 °C, whereas the other was removed to +2 to +6 °C for 8 h. Samples were assayed for fibrinogen, FVIII, VWF:Ristocetin cofactor activity (RCo), VWF:Ag and VWF:Collagen binding (CB). The cryoprecipitate fibrinogen content increased to a mean of 207 mg unit −1 . VWF:Ag, VWF:RCo and VWF:CB recoveries also increased. FVIII recovery decreased from 50 to 45% (mean 124 iu unit −1 ). Conditioning has been validated for routine production of cryoprecipitate from imported plasma.