NEFL and polyneuropathy: Therefore, this study aims to compare the performance of SiMoA and Ella in measuring serum NfL levels in symptomatic ATTRv subjects and presymptomatic ATTRv subjects, where NfL has been demonstrated to represent a reliable biomarker of nerve damage and polyneuropathy [20], to evaluate the correlation between the two methods and their reliability in detecting NfL levels in peripheral neuropathy.