The influence of methylene blue light treatment and methylene blue removal filter on fibrinogen activity states and fibrin polymerisation indices

Background-objective. Methylene blue light treatment (MBLT) is efficient in inactivating viruses in plasma. However, it may cause alterations in clotting factors, especially fibrinogen (Fg). The true mechanism of such a selective alteration is poorly understood, The effects of MBLT and MB removal filters (MBRF) on Fg concentration, functional activity and fibrin polymerisation were studied. Design. Apheresis plasma collected by Haemonetic MCS Plus (n = 10) was split into two equal aliquots. Both were leukofiltered and virally inactivated in a standardized fashion, using Theraflex MB-Plasma Photodynamic viral inactivation Macopharma method. One of the pair was subsequently processed, using Blueflex MBRF to remove residual MB and its by-products. Control plasma samples were obtained after filtration but before MBLT. Samples were also obtained after MBLT and MBRF. All samples were analyzed for the Fg activity, Fg antigen, thrombin clotting time (TT), and alterations fibrin polymerisation indices. Results. After MBLT, mean Fg concentration increased slightly (2%) whereas functional activity decreased by 31%, as compared to control samples. Mean TT prolonged by 6 s after MBLT, with no further changes after MBRF. A similar trend was observed using RT. Both thrombin and reptilase triggered fibrin polymerisation were delayed and the polymerisation curves slopes were decreased slightly, with concomitant changes in fibrin opacity in samples from MBLT and MBRF as compared to control. Comparison is made for the first time with a similar changes observed in dysfibrinogenemia. Conclusion. MBLT resulted in about 30% decrease in Fg activity but a slight modification in fibrin polymerisation indices, with no additional alteration subsequent to MBRF. These in vitro changes are similar to those seen in plasma from patients with dysfibrinogenemia, which are usually without clinical significance. (c) 2005 Published by Elsevier Ltd.