Clinical application of multigene panel testing for bleeding, thrombotic, and platelet disorders: a 3-year Belgian experience

Background: The international study ThromboGenomics has evaluated the diagnostic rate using a targeted multigene panel test for the screening of inherited bleeding, thrombotic and platelet disorders.Objectives: We retrospectively analyzed the results of the implementation of genetic testing for inherited bleeding, thrombotic and platelet disorders in Belgian clinical practice and evaluated possible reclassification of reported variants.Patients/methods: We implemented a Thrombosis-Hemostasis multigene panel test using whole exome sequencing to diagnose 487 patients recruited by 27 different Belgian hospitals with the implementation of stringent laboratory accreditation stan-dards and by studying up to 100 diagnostic-grade genes.Results: This Thrombosis-Hemostasis multigene panel test was able to detect at least one genetic variant in 58% of the 487 patients of which 50% were (likely) pathogenic variants and the others were variants of unknown significance. Polygenic variants were detected in 65 patients (13%). A multi-step workflow for results discussion by multi-disciplinary team meetings and patients' recalls for segregation studies and additional laboratory testing was set up. Variants were also submitted to the GoldVariants database from the International Society on Thrombosis and Haemostasis (ISTH). The aim of these approaches is to optimize variant interpretation and to (re)classify variants of unknown significance as (likely) pathogenic or (likely) benign.Conclusions: The growing implementation of multigene panel tests in clinical di-agnostics comes with difficulties in interpreting genetic results. Additional efforts are needed to continuously optimize the diagnostic outcome.