Venous thromboembolism laboratory testing (factor V Leiden and factor II c.*97G>A), 2018 update: a technical standard of the American College of Medical Genetics and Genomics (ACMG).

Factor V Leiden and factor II c.*97G>A (formerly referred to as prothrombin 20210G>A) are the two most common genetic variants associated with venous thromboembolism (VTE). Testing for these variants is one of the most common referrals in clinical genetics laboratories. While the methodologies for testing these two variants are relatively straightforward, the clinical implementation can be complicated with regard to test indications, risk assessment of occurrence and recurrence of VTE, and related genetic counseling. This document provides an overview of VTE, information about the variants and their influence on risk, considerations before initiating genetic testing, and the clinical and analytical sensitivity and specificity of the tests. Key information that should be included in the laboratory report is also provided. Disease-specific statements are intended to augment the general American College of Medical Genetics and Genomics (ACMG) technical standards for clinical genetics laboratories. Individual laboratories are responsible for meeting the Clinical Laboratory Improvement Amendments (CLIA)/College of American Pathologists (CAP) quality assurance standards with respect to appropriate sample documentation, assay validation, general proficiency testing, and quality control measures. This 2018 edition of the ACMG technical standard updates and supersedes the 2005 edition on this topic. It is designed to be a checklist for genetic testing professionals who are already familiar with the disease and the methods of analysis.