For diagnostic CFTR testing, variants in the polymorphic TG/T tract are analyzed, interpreted and only reported if classified as “Likely pathogenic,” or “Pathogenic.” The 5T is classified as Pathogenic and would be included, if present. The benign polymorphisms, 7T and 9T, and uncertain variants are not included in the primary report but are available upon request.
For carrier screening, when the 5T variant is present in conjunction with 11TG, 12TG, or 13TG, it will be reported. We do not report the presence of 5T if it is in conjunction with any other TG tract variant (e.g. 10TG). A 5T variant is always associated with a specific number of TGs in the gene. Some TG numbers (11, 12, 13) are known to be problematic (to different degrees) while others (10) are not thought to be pathogenic.