Filtration of methylene blue-photooxidized plasma : influence on coagulation and cellular contamination

BACKGROUND: Virus inactivation of plasma can be achieved by photodynamic methods in the presence of phenothiazine dyes such as methylene blue (MB). Subsequent filtration may increase the efficacy of virus inactivation and reduce adverse effects of WBC contamination and MB. STUDY DESIGN AND METHODS: This study examined the effect of filtration with three different filters (MBF1, MBF2, and MBF3) on MB concentration, residual cells, coagulation factors, and activation measures of coagulation, fibrinolysis, and complement in MB-treated (1 μM/L) plasma units. RESULTS: Filtration reduced the concentration of MB by ≥89 percent. WBCs were depleted by 92 percent (MBF1) and >99.9 percent (MBF2 and MBF3). Treatment with MB significantly decreased the coagulation potency from levels in untreated plasma, as measured by thromboplastin time ratio (112 ± 18% vs. 95 ± 11%), activated partial thromboplastin time (40 ± 3 sec vs. 44 ± 3 sec), thrombin time (16.9 ± 1.1 sec vs. 18.6 ± 1.5 sec), factor VIII (1.09 ± 0.21 U/mL vs. 0.85 ± 0.13 U/mL), and vWF (0.94 ± 0.65 U/mL vs. 0.65 ± 0.24 U/mL). Filtration did not further decrease these values, while factor XI (0.75 ± 0.22 U/mL vs. 0.37 ± 0.20 U/mL) and prekallikrein values decreased in MB plasma units filtered with the MBF3. In addition, activated factor XII (0.7 ± 0.5 μg/L vs. 4.5 ± 1.0 μg/L) increased. CONCLUSION: WBCs and MB can be eliminated from MB-treated plasma units by filtration. Differences in biocompatibility of the different filters, especially the influence on the contact phase of coagulation, must be taken into consideration.