In vitro evaluation of prestorage pools consisting of mixed A and O platelet concentrates

Current FDA regulations allow the prestorage pooling of whole blood-derived platelet concentrates (PCs) of identical ABO type in a recently cleared platelet (PLT) pooling bag (Acrodose, Pall Medical). It is unclear how ABO-mixed PC pools would store if pooled before storage.

Pools consisting of ABO-identical PLTs and mixed A and O PLTs in varying proportions were evaluated on Days 1, 5, and 7 of storage with measures of the PLT storage lesion, lymphocyte activation, and activation of the complement and coagulation system. Data were analyzed by analysis of variance.

Pools did not differ on Day 7 in pH (p = 0.63), hypotonic shock response (p = 0.25), extent of shape change (p = 0.26), morphology score (p = 0.18), or white cell count (p = 0.79), but surface P-selectin expression was more evident in the ABO-mixed pools (p = 0.02). Small microscopic clumps of PLTs were observed in all pools, but were more prominent in the ABO-mixed pools (p < 0.01). PLT counts, however, did not differ between pools (p = 0.93), indicating that only a small proportion of PLTs were clumped. Surface A-antigen expression was proportional to the number of A PCs in each pool and did not vary between study days. Anti-A(1) titers were either unchanged or decreased by one dilution. Complement and coagulation activation markers did not differ between pools.

Pooling A and O PCs is associated with evidence of increased microscopic PLT clumping and activation, but these differences are not exacerbated with 7-day storage. Other major measures of PLT quality do not differ, and there was no evidence of a mixed lymphocyte reaction.