Molecular Genetics Platelet Disorders Panel

Inherited platelet disorders are a group of genetic conditions that cause excessive and uncontrollable bleeding. While variable in severity, these conditions can potentially cause life-threatening complications following surgery, childbirth, trauma, or internal hemorrhages. Pathogenic variants in genes encoding cytoskeletal proteins, platelet adhesions and signaling pathways triggering coagulation are analyzed in this next-generation sequencing-based panel test. The test also includes genes associated with Bernard-Soulier syndrome, Scott syndrome, Glanzmann’s thrombasthenia, Thromboxane A2 receptor deficiency, GP6 collagen receptor deficiency, and Hermansky-Pudlak syndrome. The overall incidence for inherited platelet disorders is estimated to be ~1:10,000 (Maclachlan et al., 2016). Platelet disorders can be inherited in an autosomal recessive, autosomal dominant, or X-linked manner, which is dependent upon the causative gene.  

The genes included in this panel were curated in collaboration with the OHSU Hemostasis and Thrombosis Center, including director Dr. Kristina Haley, an expert in diagnosis and medical management of bleeding and clotting disorders. For clinical consultation with the Hemostasis and Thrombosis clinical team, please call 503-494-8716 or visit the OHSU Hemostasis and Thrombosis Center website for further information.

Reasons for Referral:

• Abnormal bleeding or bruising
• Uncontrollable bleeding
• Positive family history for bleeding disorders (targeted testing is available if familial mutation is known.)
• Inherited thrombocytopenia
• Abnormal hemostatic functional testing

Genomic DNA is analyzed using next-generation sequencing (NGS) on the Illumina NextSeq 2000 platform, with target enrichment performed using hybridization-based probes to capture exonic (coding) regions of the gene(s). Single nucleotide variants (SNVs) and small insertions or deletions (INDELs) are identified using the Illumina DRAGEN Enrichment Workflow, executed onboard the NextSeq2000. This pipeline combines software and hardware acceleration to generate high-confidence germline haplotype calls. Clinical and analytical validation of DRAGEN was performed in our laboratory. Based on validation study results, for SNVs, this assay achieves >96% analytical sensitivity and >99% positive predictive value (PPV). For INDELs <50 bp, the analytical sensitivity is >87% and the PPV is >97%. INDELs >50 bp may be detected but the sensitivity for these is reduced.

Exon-level copy number variants (CNVs) are detected using the Germline Copy Number Variation Best Practices pipeline from GATK. A Bayesian model, clinically validated in our laboratory, enables detection of deletions and duplications involving three or more contiguous exons in genes with adequate probe coverage and without complicating factors (e.g. pseudogene homology, short tandem repeats, segmental duplications). Please note that exon-centric microarray remains the gold standard for exonic copy number variant calling. If exon-centric microarray is of interest, please contact the laboratory for additional information.

Blood:  EDTA or ACD (Solution A or B):

• Adult: 5 mL
• Child: 5 mL
• Infant: 2-3 mL

Saliva: 2 ORAgene™ Saliva Collection Kits (OGR-500) used according to manufacturer instructions.  Please contact KDL Client Services for a Saliva Collection Kit for patients that cannot provide a blood sample.

Assisted Saliva: 4 ORAgene™ Assisted Saliva Collection Kits (OGR-575) used according to manufacturer instructions.  Please contact KDL Client Services for an Assisted Saliva Collection Kit for patients that cannot provide a blood sample.

Buccal Cells: 4 CytoSoft™ Cytology Brush (Medical Packaging CYB-1) used according to manufacturer instructions.  Please contact KDL Client Services for a Buccal Collection Kit for patients that cannot provide a blood sample.

Skin Fibroblast: Punch Biopsy (Cell cultures will be prepared at KDL and used for testing), or 2 T-25 confluent flasks.

DNA: 5-10µg at a minimum of 60-100ng/µL (DNA must be extracted in a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by the CAP and/or CMS).

For routine testing of blood, saliva and buccal swabs, KDL does NOT accept samples from patients within two (2) weeks of a packed cell/platelet transfusion or within four (4) weeks of a whole blood transfusion.  For extraordinary circumstances, where testing must be performed within the above windows, please contact our lab.

For patients with bone marrow transplants, the only acceptable specimen type is a skin biopsy (Cell cultures will be prepared at KDL before testing).

Weekly

6-8 weeks

• Package and ship specimen to remain cold, but not frozen. 
• Ship via overnight express, using the FedEx priority overnight label provided. 
• Contact Client Services for shipping kits and instructions at (855) 535-1522.

1. Chen, D., & Pruthi, R. K. (2023). Platelet genetic testing by next‐generation sequencing: A practical update. International Journal of Laboratory Hematology, 45(5), 630–642. 
2. Clinical Genome Resource. https://clinicalgenome.org/affiliation/40028
3. International Society on Thrombosis and Haemostasis (ISTH) SSC on Genomics in Thrombosis and Hemostasis. (2024). ISTH Tier 1 Gene List (v. ISTH_2024.1). Gold Variants - International Society on Thrombosis and Haemostasis. Retrieved from https://www.isth.org/page/GinTh_GeneLists
4. Kopanos, C., Tsiolkas, V., Kouris, A., Chapple, C. E., Aguilera, M. A., Meyer, R., & Massouras, A. (2019). VarSome: the human genomic variant search engine. Bioinformatics, 35(11), 1978–1980. 
5. Maclachlan, A., Watson, S. P., & Morgan, N. V. (2016). Inherited platelet disorders: Insight from platelet genomics using next-generation sequencing. Platelets, 28(1), 14–19. 
6. Palma-Barqueros, V., Revilla, N., Sánchez, A., Zamora Cánovas, A., Rodriguez-Alén, A., Marín-Quílez, A., González-Porras, J. R., Vicente, V., Lozano, M. L., Bastida, J. M., & Rivera, J. (2021). Inherited platelet disorders: An updated overview. International Journal of Molecular Sciences, 22(9), 4521.