P57 How Many Donors with Transfusion Microbiology False Positive Results Return to Give Samples for Re‐entry.

Donors who falsely react in any of the transfusion microbiology screen tests are sent a standard letter and asked to give a sample after a suspension of twelve weeks [84 days]. The donors can then be considered for re‐entry to the active panel. We are not aware of any work showing how many donors re‐attend to give samples and how soon, so have analysed our national figures. 1301 donors who donated in the 3 months from 1st Oct 05 [434 per month] gave a false positive reaction and were sent the standard letter. 2269 donors returned in the period 1st Jan 06 to 31st May 06 [453 per month] following the standard letter and gave samples to be considered for re‐entry. Of these: 769 had donated in the 3 months from 1/10/05, 393 females and 376 males. The average number of days between initial and repeat samples was 130 days for females and 129 days for males with standard deviations of 27.4 and 27.9. Two donors attended and were sampled at less than 84 days! We recorded a maximum time interval between sample and donation of 231 days ‐ with each testing centre having donors attending at over 150 days. 755 donors were returned to the active panel [400 using the alternative assay re‐entry algorithm]. We have shown that 59% of false positive donors have given further samples for re‐entry. The figure is constrained by the length of time for which data is currently available. It may be higher if data were available for a longer period. When more data are available it may be possible to investigate how many false positive donors do not return and compare the results with those for first time donors, currently approximately 30%.