Genetic screening by high-throughput sequencing

High-throughput sequencing (HTS) techniques for targeted gene panels based on whole exome sequencing (WES) or whole genome sequencing (WGS) have now largely replaced Sanger sequencing and linkage analysis that were performed in the past.

We recommend for IPD diagnosis that HTS should be performed using a validated gene panel of curated, diagnostic-grade genes (genes in which variants have been proven to cause human disease, for example through biochemical studies or segregation with the phenotype in at least four independent pedigrees; as recommend by the ISTH) [1].

A diagnostic rate of approximately 50% in patients with suspected inherited thrombocytopenia and up to 25% in patients with a known platelet function disorder confirmed by laboratory tests can be obtained by HTS [2,3].

We suggest that genetic screening may be considered in patients with any of the following:

a suspected hereditary thrombocytopenia
syndromic features
a strong family history
a significant bleeding score (ISTH-BAT) or bleeding pattern (e.g., minor surgery or epistaxis that results in hospitalization and/or transfusion and/or menorrhagia) and where clinical and/or laboratory features strongly suggest a platelet disorder, but where further diagnostic assays are not available.

Genetic analyses should also be considered for confirmation of diagnosis of severe bleeding disorders such as Glanzmann’s thrombastenia and Bernard Souliers syndrome.

Interpretation of results from genetic screening

Usually, several candidate disease-causing DNA variants are identified when using HTS technology. Correct interpretation and pathogenicity scoring of these variants are crucial for diagnosis and appropriate genetic counselling.

We recommend that samples for genetic testing should be sent to a genomic center with expertise in bleeding/platelet disorders.

We recommend that the center should not only report previously reported variants, but be able to report variants that by functional testing and segregation analyses can be proven to be pathogenic (see attachment “Interpretation of Results from Genetic Screening”). We strongly recommend that the center should provide a multidisciplinary team comprising of clinicians with expertise in bleeding/platelet disorders, geneticists, coagulation/platelet laboratory specialists, and bioinformaticians with the capacity to classify candidate disease causing variants [4,5]. At the time of writing, the Department of Genomic Medicine, Copenhagen University Hospital, Denmark and the Adult/Pediatric Coagulation Unit, Karolinska University Hospital, Stockholm, Sweden can provide this service in the Nordic countries.

We recommend that likely pathogenic or pathogenic variants are submitted to the ISTH Goldvariant database [6,7].

Patient information at the time of genetic testing

It is important that the patient understands the testing procedure, the benefits and limitations of the test, and the possible consequences of the test results in relation to clinical management options [8].

We recommend informing the patient of the possibility of incidental findings and also of the risk of finding variants indicating risk for malignant hematological disease. Patients should also be informed, both prior to and following testing on the importance of discussing potential genetic testing results with their relatives. We recommend that clinicians inform about the possibility of anonymized sharing of data to provide a greater understanding of the relevance of particular genetic variants enabling to improve molecular diagnosis in patients with similar conditions in the future. Of note, very few variants are published for the majority of the ISTH Goldvariants IPD Tier-1 genes. This implies that genetic screening may uncover a large number of previously not described variants.

For further details see and examples of patient information used in the Nordic countries see attachment: “Patient information” as well as:

For genetic screening, samples (EDTA whole blood) and a detailed patient history can be sent to:

Dept. of Genomic Medicine, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark

Email: gmsekretariat.rigshospitalet@regionh.dk

Adults: Koagulation mottagning, A 10:01

Eugeniavägen 3, Solna

Karolinska Universitetssjukhuset

171 76 Stockholm

Children: Barnkoagulation mottagning, A10:03

Eugeniavägen 3, Solna

Karolinska Universitetssjukhuset

171 76 Stockholm

Megy K, Downes K, Simeoni I, Bury L, Morales J, Mapeta R, et al. Curated disease‐causing genes for bleeding, thrombotic, and platelet disorders: Communication from the SSC of the ISTH. Journal of Thrombosis and Haemostasis 2019;17:1253–60. doi:10.1111/jth.14479.

Freson K, Turro E. High‐throughput sequencing approaches for diagnosing hereditary bleeding and platelet disorders. Journal of Thrombosis and Haemostasis 2017;15:1262–72. doi:10.1111/jth.13681.

Vears DF, Sénécal K, Borry P. Exploration of genetic health professional - laboratory specialist interactions in diagnostic genomic sequencing. European Journal of Medical Genetics 2020;63:103749. doi:10.1016/j.ejmg.2019.103749.

Downes K, Megy K, Duarte D, Vries M, Gebhart J, Hofer S, et al. Diagnostic high-throughput sequencing of 2396 patients with bleeding, thrombotic, and platelet disorders. Blood 2019;134:2082–91. doi:10.1182/blood.2018891192.

Leinøe E, Zetterberg E, Kinalis S, Østrup O, Kampmann P, Norström E, et al. Application of whole‐exome sequencing to direct the specific functional testing and diagnosis of rare inherited bleeding disorders in patients from the Öresund Region, Scandinavia. British Journal of Haematology 2017;179:308–22. doi:10.1111/bjh.14863.

Megy K, Downes K, Morel‐Kopp M, Bastida JM, Brooks S, Bury L, et al. GoldVariants, a resource for sharing rare genetic variants detected in bleeding, thrombotic, and platelet disorders: Communication from the ISTH SSC Subcommittee on Genomics in Thrombosis and Hemostasis. Journal of Thrombosis and Haemostasis 2021;19:2612–7. doi:10.1111/jth.15459.

Downes K, Borry P, Ericson K, Gomez K, Greinacher A, Lambert M, et al. Clinical management, ethics and informed consent related to multi‐gene panel‐based high throughput sequencing testing for platelet disorders: Communication from the SSC of the ISTH. Journal of Thrombosis and Haemostasis 2020;18:2751–8. doi:10.1111/jth.14993.

Gomez K, Laffan M, Keeney S, Sutherland M, Curry N, Lunt P. Recommendations for the clinical interpretation of genetic variants and presentation of results to patients with inherited bleeding disorders. A UK Haemophilia Centre Doctors’ Organisation Good Practice Paper. Haemophilia 2019;25:116–26. doi:10.1111/hae.13637.