The United Kingdom National External Quality Assessment Scheme (blood transfusion laboratory practice): trends in proficiency and practice between 1985 and 2000.

Proficiency in blood transfusion laboratory practice has improved over the last 15 years (1985-2000). Error rates for ABO grouping have fallen from 0 x 19 to 0 x 02% (P = 0 x 003). A similar trend is evident for antibody screening, with error rates for false negative antibody screens falling from 3 x 2 to 0 x 5% (P < 0 x 001), and for antibody identification, for sera containing a single alloantibody, with error rates falling from 8 x 8% to 0 x 9% over the last 10 years (P < 0 x 001). Proficiency in serological crossmatching to detect clinically significant non-ABO incompatibilities (other than Kidd), has also improved (P < 0 x 001). However, error rates for RhD grouping have not changed and there has been a recent decline in proficiency in detecting weak ABO incompatibilities and Kidd antibodies with heterozygous cells. Procedures for pretransfusion testing have also been rationalized over this time. The indirect antiglobulin test (IAT) is used in isolation by 73% of laboratories for antibody screening, and 10% rely on the direct room temperature (DRT), immediate spin (IS) crossmatch in the absence (current and/or historical) of clinically significant antibodies. Despite the improvements in error rates that have occurred alongside the rationalizations, there is still evidence of noncompliance with current published BCSH guidelines and manufacturers' instructions.