Assessment of the correlation of platelet morphology with in vivo recovery and survival

BACKGROUND:  There is continuing interest in the development of in vitro tests evaluating the in vivo function, recovery, and survival of platelets stored for transfusion. A recent forum concluded that no completely reliable test exists, although discoid morphology indicates a platelet's good health. We evaluated a novel device, the NAPSAC (Noninvasive Assessment of Platelet Shape and Concentration), designed to determine noninvasively the proportion of discoid platelets in a stored concentrate, as well as platelet concentration.
STUDY DESIGN AND METHODS:  Twenty-eight plateletapheresis concentrates stored 24 hours in PL-146 were evaluated. Percent discoid platelet results were correlated with radiolabeled autologous recovery and survival performed using 111Indium oxyquinoline and calculated using linear (L) and multiple-hit (M) models. pH of 8 concentrates was raised at the end of storage with 6N NaOH. Platelet concentration measured by NAPSAC and Coulter Thrombocounter C was compared in 256 plateletapheresis products.
RESULTS:  Percent discoid platelets at 24 hours did not correlate significantly with platelet recovery or survival (recovery L = 0.29, M = 0.28; survival L = 0.16, M = 0.03). Raising the pH (mean 6.38 to 6.94) resulted in a significant increase in percent discoid platelets (21% to 41%). Platelet concentration values for both methods studied were linearly correlated with a slope of 1.01 ± 0.03, r = 0.81.
CONCLUSION:  Percent discoid platelets was not predictive of posttransfusion platelet recovery or survival. The results suggest that non-discoid platelets may survive posttransfusion and even revert to discoid shape, since raising the pH approximately doubled the percent of discoid platelets. The NAPSAC was shown to be a reliable instrument for noninvasively determining platelet concentration in PL-146 concentrates.