Analysis for a familial variant can be performed using either Sanger sequencing or Next Generation Sequencing (NGS). Sanger sequencing is only able to detect levels of heteroplasmy above 20% while NGS can detect levels as low as 10%. For this reason, Sanger sequencing may be considered as a first step in evaluating for the presence of a familial variant. NGS testing may be reserved for those who appear to be affected or who would be expected to carry the familial variant, but have had negative Sanger sequencing results. As heteroplasmy levels vary from tissue to tissue, a negative blood test cannot completely rule out the chance that an individual carries the familial variant.