Proficiency testing for HLA-DRB high-resolution typing: a 4-year experience in Italy.

Twenty-one Italian laboratories participated for four consecutive years in the collaborative Italian proficiency testing of HLA class II (DRB1, DRB3, DRB4 and DRB5) high-resolution typing. In this paper the results are analysed. Seven different kinds of errors are described and discussed. The errors were divided into technical errors and errors of allele reporting. Each year, a list of errors made was prepared by our laboratory and discussed collegially with all laboratories. The allele reporting errors diminished over time, as a result of the common discussions. The technical performance of the laboratories did not improve overall for the 21 laboratories participating: for 16 of them results were good or improved in quality, but for the remaining five results deteriorated over time. From this experience, some recommendations for the future emerged. A relevant conclusion was that, to improve the performance of a group of laboratories, the proficiency test is not effective alone, but should be integrated within a framework of continuous collaboration and mutual technical help.