AbstractBackground and ObjectivesBased on previous success using apheresis platelets, we wanted to investigate the in vitro quality and platelet function in continuously cold‐stored and delayed cold‐stored platelet concentrates (PCs) from interim platelet units (IPUs) produced by the Reveos system.Materials and MethodsWe used a pool‐and‐split design to prepare 18 identical pairs of PCs. One unit was stored unagitated and refrigerated after production on day 1 (cold‐stored). The other unit was stored agitated at room temperature until day 5 and then refrigerated (delayed cold‐stored). Samples were taken after pool‐and‐split on day 1 and on days 5, 7, 14 and 21. Swirling was observed and haematology parameters, metabolism, blood gas, platelet activation and platelet aggregation were analysed for each sample point.ResultsAll PCs complied with European recommendations (EDQM 20th edition). Both groups had mean platelet content >200 × 10⁹/unit on day 21. The pH remained above 6.4 for all sample points. Glucose concentration was detectable in every cold‐stored unit on day 21 and in every delayed cold‐stored unit on day 14. The cold‐stored group showed a higher activation level before stimulation as measured by flow cytometry. The activation levels were similar in the two groups after stimulation. Both groups had the ability to form aggregates after cold storage and until day 21.ConclusionOur findings suggest that PCs from IPUs are suitable for cold storage from day 1 until day 21 and delayed cold storage from day 5 until day 14.