Correlation of in vitro platelet quality measurements with in vivo platelet viability in human subjects.

BACKGROUND AND OBJECTIVES Changes in in vitro platelet quality parameters during platelet storage are associated with a decrease of in vivo platelet viability after platelet transfusion. Many attempts have been made to identify the most predictable in vitro parameters for in vivo performance. We used a riboflavin-based ultraviolet (UV) light treatment process designed to inactivate pathogens and white blood cell (WBC) contaminants in blood products as a model system in which to study the correlation of in vitro cell quality with in vivo viability. MATERIALS AND METHODS Platelet products (n = 18) were collected by a standard Trima apheresis procedure and treated with one of three dose levels of UV light (0, 7.2 or 12.4 J/ml) in the presence of 50 microm riboflavin. Lactate production, glucose consumption and P-selectin expression, pH, pCO(2), pO(2), hypotonic shock response and swirl were measured during 5 days of platelet storage post-UV/RB treatment. Aliquots of these products were radiolabelled on day 5 of storage and were subsequently used to determine platelet recovery and survival time in autologous subjects. RESULTS The responses of in vitro cell quality were observed to occur in a UV dose-dependent manner. Lactate production and pH were identified as the parameters most strongly correlated with platelet in vivo recovery, which ranged from 5 to 82%. The correlation coefficients (r) for lactate production and pH with in vivo recovery in human subjects were 0.9090 and 0.8831 with P-values of 0.007 and 0.031, respectively. Lactate production and pH were also found to be correlated with platelet survival time, with correlation coefficients of 0.8063 and 0.8384 (the P values were 0.01 and 0.001, respectively). CONCLUSIONS Using conditions of riboflavin-based UV light treatment, lactate production and pH were identified as having the highest correlations with recovery and survival of radiolabelled platelets in healthy subjects.