A multicenter inspection of the swirling phenomenon in platelet concentrates prepared in routine practice

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Abstract
In a previous multicenter study, the absence of the swirling phenomenon correlated well with platelet disc-to-sphere transformation, a morphology feature associated in the past with poor platelet viability. In 13 centers, 5366 platelet concentrates (PCs) were prepared and stored under routine conditions and evaluated for the presence of swirling. PCs found not to have swirling were evaluated for pH and platelet and white cell counts in parallel with an equal number of PCs with swirling that were studied as controls. In 13 participating centers, swirling was reported to be absent after 3 and 5 days of storage in 0 to 3.8 percent and in 0 to 18 percent of PCs, respectively. In 94 percent of units with swirling, pH was 6.7 to 7.5; this is a range of values associated with adequate in vivo survival. In 69 percent of PCs without swirling, pH was lower than 6.4 or higher than 7.6; these values are associated with reduced platelet viability. Three-quarters of the cases in which the absence of swirling was associated with pH values between 6.7 and 7.5 were reported from 2 out of the 13 participating centers. In PCs prepared and stored under routine conditions, the presence of swirling correlated well with pH values associated with adequate platelet in vivo viability. In about 20 percent of PCs without swirling, this was not due to a low or high pH value, and it would be useful to investigate whether this lack of swirling is associated with poor platelet viability. These data support the possibility that the evaluation of swirling by visual inspection might replace invasive and more cumbersome assays currently used for routine PC quality control.