When the Donor Is the Root Cause: Platelet Concentrate Quality Control Failure Due to Constitutional Macroplatelets Detected During a Vertical Audit

Quality control (QC) failure of a whole blood-derived platelet concentrate (PC) is usually attributed to process-related factors, such as centrifugation settings, separation technique, holding time, or storage conditions.We report an isolated PC QC failure in which the root cause was traced to donor platelet morphology.During the first vertical audit of component preparation at our newly established blood centre, four whole blood units processed by the platelet-rich plasma (PRP) method were prospectively traced.One PC showed absent swirling during processing and contained only 5 × 10³ platelets/µL in 55 mL, corresponding to a yield of 0.03 × 10¹⁰ (2.75 × 10⁸) platelets, far below the regulatory requirement of ≥4.5 × 10¹⁰.By contrast, the three PCs processed concurrently had platelet yields of 5.40-6.69× 10¹⁰ and met QC requirements.The index donor was a 42-year-old male with a normal pre-donation platelet count (356 × 10³/µL), but the mean platelet volume (MPV) was elevated (12.4 fL), with a platelet-large cell ratio (P-LCR) of 43.7% and an analyser flag for giant platelets.Peripheral smear examination demonstrated numerous large and giant platelets.Component tracing revealed that only 0.17% of the donor's circulating platelets were recovered in the PC, compared with 47.4-71.8% in the other three units.Conversely, 26.0% of the donor's platelets were retained in the packed red cell component, compared with 4.4-13.0% in the other units.Furthermore, the few platelets recovered in the PC were smaller, with an MPV of 9.5 fL and P-LCR of 18.7%, compared with 12.4 fL and 43.7% in the donor's whole blood sample.These findings suggest sizedependent co-sedimentation of macroplatelets with red cells during the soft-spin step of PRP preparation, resulting in markedly reduced platelet recovery in the PC.The donor had no bleeding history, and macroplatelets persisted on repeat testing.This case highlights that donor-related platelet morphology can be an important and overlooked cause of isolated PC QC failure.Evaluation of platelet indices and peripheral smear morphology should therefore be considered during root cause analysis of an unexpected, isolated PC failure, particularly in populations where constitutional macroplatelet disorders may occur.