This report is being filed to provide additional information and investigation: the whole blood collection set was not returned to terumo bct for evaluation.The manufacturing records, test records, and inspection records for the reported lot number were reviewed for abnormalities and none were found.In addition, the dope material used were investigated and found that the viscosity of pu solution of dope material conformed to the standards.The records regarding the particulate removal rates of the filter membranes of the reported lot number were reviewed and 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: a definitive root cause for the observed elevated wbc count remains undetermined at this time.Based on the available information, it cannot be ruled out that the higher-than-expected wbc content in the whole blood product could be due to an occlusion,blood may have been filtered by a smaller than usual filter area.As a result, linear speed may have increased, and leukocyte leakage may have occurred.As an increase of wbc contamination complaints were noted from previous lot numbers, further investigation was performed.Investigation results indicated that the cause of higher-than-expected wbc content in the whole blood product was due to the maximum pore size of the filter membrane is likely to increase according to the combination of multiple parameters in manufacture of leukoreduction filter membranes and wbc contamination is likely to occur frequently in the product lots of which the maximum pore size of the filter membrane has increased.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.Corrective action: an internal capa has been initiated to review the maximum pore size of the filter membrane and the likelihood of an increase according to the combination of the multiple parameters.In addition, the wbc contamination is likely to occur frequently in the product lots of which the maximum pore size of the filter membrane has increased.To achieve a resolution, manufacturing specifications were updated to narrow the range of the parameters in the manufacture of filter membranes and it was confirmed that the appropriate level of the maximum pore size of the filter membrane was achieved.
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