This question may be mainly for UK Blood Transfusion labs, but we have just had an ISO 15189 inspection and our inspector says we should be doing Uncertainty of Measurement (UoM) in Blood Transfusion labs, especially with regards to Blood grouping. Now, I have no idea how UoM relates to Blood Bank procedures, and my inspector failed to convince me, but he said that this is quite common in the UK now and many Transfusion labs are doing this. So for anyone working in a UK Blood Bank who are ISO 15189 accredited, are you doing UoM calculations for any BB procedure? If you are, can you please explain to me how it is relevant and what are you actually doing? UoM is relevant to Haematology and Chemistry with all their CVs and SDs and Bias calculations etc, but what the heck has it got to do with Blood Bank work!