This report is being filed to provide additional information in h.3, h.6 and h.10.Investigation: one set of blood bags with the filter from the collection set was returned for evaluation.The leukoreduction filter was tested for flow rate and air leaks.A slow flow rate of 10ml/min was noted, and it was confirmed there were no air leaks.The filter was disassembled to observe the appearance of filter membranes and noticed creases in the filter membranes of the filter.The creases in the filter were not different from those in conforming products and in the filter membranes and aggregation was observed in the first filter membrane.The manufacturing records, test records, and inspection records were reviewed for abnormalities and none were found.The records regarding the particulate removal rates of the filter membranes were reviewed.All membranes conformed to established specification.Shipping testing was performed on the reserve samples from the reported lot number.The reserve samples were also visually examined, and the solution volume and solution composition were tested with no abnormalities noted.All product conformed to the established specification.Root cause: the above-mentioned investigation results revealed that there were no abnormalities in the manufacturing record and the testing and inspection record of the reported lot number.The returned filter also revealed no abnormalities in itself.We noticed that the first, second, and fourth filter membranes were dyed dark with toluidine blue.Therefore, occlusion may have occurred and blood may have been filtered by the filter area which was smaller than usual and the linear speed (flow rate per unit area) increased, and then leukocyte leakage occurred.In addition, we observed aggregation in the first filter membrane in the filter.We therefore infer that excessive aggregates in the donation bag flowed into the filter after the start of filtration and caused clogging on the inflow side of the filter layers.There is also a possibility that the blood may have been separated in the donation bags and the separated blood did not disappear even after being agitated prior to filtration.As a result, the blood with high flow resistance flowed into the filter and occluded the inflow side of the filter layers; therefore, leukocyte leakage may have occurred by the increase in the linear speed due to occlusion in the areas with aggregation.The instructions for use provide a caution to not squeeze or apply pressure to the filter while it is attached to the bag containing the filtered blood and also to clamp the blood-filled tubing before blood enters the filter in order to avoid leukocyte leakage.
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