FA is caused by a variant within the FXN gene called a GAA triplet-repeat expansion.3 Nearly all cases (96%) are caused by this variant in both alleles, while about 4% are attributable to a second FXN mutation.3 A genetic test that includes a GAA triplet-repeat expansion analysis is the only way to confirm an FA diagnosis.1
Most major diagnostics companies offer testing that can detect FA, whether it is caused by a GAA triplet-repeat expansion or a point mutation.
Only a genetic test that includes a GAA triplet-repeat expansion analysis can detect pathogenic repeat expansion variants. Standard multigene panels that include only a sequence analysis cannot detect the triplet-repeat expansion variants.1
One way to determine the anticipated severity of FA is by identifying the number of GAA triplet repeats.4 Currently, only an FA repeat expansion analysis that includes sizing of the repeat expansion can give you this information.
Whether you use a multi- or single-gene test, confirm that the test includes a GAA repeat-expansion analysis, which may be denoted by the CPT code 81284.1,5