**5. Accreditation**

Flow cytometry is a highly versatile and complex technology, which is routinely applied in clinical diagnostic laboratories. The vast majority of assays are laboratory developed tests based on publications, without any gold standard reference [30] mostly with poor validation. For the purpose the ICSH/ICCS workgroup published in 2013 the practice guidelines for validation of cell-based fluorescence assays [31], subsequently several relevant publications addressed various aspects of the validation of PNH testing by flow cytometry [12, 13, 32]. Each laboratory applying for ISO 15189 accreditation should confirm optimal validation of instrument setup, assay performance characteristics, laboratory information system and result reporting [33].
