Measurement of transmitted light as an indicator of cryopreserved platelet viability.

This study was designed to establish an alternative technique to the morphology scoring method described by Kunicki et al. [Transfusion 1975;15:414-421] using light transmission. A reference scale for platelet quality (expressed as a percentage of fresh cells) was established with a mixture of fresh platelets and damaged platelets frozen without cryoprotectant. The transmittance, read against autologous plasma, was compared to morphology, hypotonic stress response (HSR) and ADP-induced aggregation. The results showed that transmittance, morphology and HSR were related linearly to the percentage of fresh platelets. There was a significant correlation between relative transmittance (RT) and morphology (r = 0.932), and RT and HSR (r = 0.91), but a very poor correlation was found between transmittance and aggregation. Measurements of transmittance provided an estimation of the global aspect of a population of cryopreserved platelets in terms of shape, size and composition, and the relative transmittance of a sample to that of the fresh population could predict morphology and HSR. It is concluded that these measurements offer a valid alternative method to the subjective morphology scoring obtained with cryopreserved platelets.