The PNH French Working Group Experience: Building a Strong Network of Cytometrists

The PNH working group was created in 2010 to initiate a workshop on testing white blood cells to share international recommendations.

Thirty-five French and Belgian laboratories equipped with 2- or 3-laser cytometers applied three different panels with or without FLAER reagent in 305 samples. This multicenter study demonstrated the interplatform applicability of setting harmonization and the benefits of using a harmonized gating method. A 10^-4 limit of detection was achieved with harmonized multiparametric approaches in both six-color combinations, as well as a robust quantification of minor PNH clones.

Following this workshop, the group has developed a quality control scheme since 2013 to improve PNH diagnosis practices. This annual program includes two surveys, a virtual one and one based on fresh whole-blood sample analysis. Over the last 10 years, the regular participation of the French-speaking registered centers has demonstrated their strong commitment to our program, which offers various PNH clinical situations. Alongside, the conformity of the final reports provided by the participants has increased to 96%.

In 2016, our PNH working group initiated a nationwide multicenter prospective observational study, collecting all PNH cases or GPI-deficient cells above 0.01% to monitor the long-term evolution of minor PNH clones < 1% and to further investigate the relevance of classifying type II and type III PNH cells in WBCs in clones > 1%. The strong network of cytometrists built led us to create in 2018 the French-speaking flow cytometry association in Hematology, namely CytHem, to harmonize the diagnostic practices in various hematological diseases.