Investigation: one 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 25ml/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 second filter membranes.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: 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, we noticed that the second through fourth filter membranes from the inflow side of the filter were locally dyed dark with toluidine blue.The investigation showed aggregation on the second filter membrane.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.Investigation results showed that aggregation is observed in some of the filter membranes in each filter inferring that after the filtration starts ,the excessive aggregates in the donation bags flowed into the filters 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,as it is observed that separated blood did not disappear even after being agitated prior to filtration.As a result, the blood with high flow resistance flowed into the filters and occluded the inflow side of the filter layers causing leukocyte leakage by the increase in the linear speed.The instructions for use of product state 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.Correction:in order to reduce the risk of formation of blood aggregation,it is recommended that donation bag needs to be inverted several times immediately after blood collection to ensure that blood and anticoagulant became well-mixed and to reduce the risk of slow blood flow the bag should be fully agitated before the start of filtration for the even disperse of the separated blood components.
|