The present study demonstrates that frataxin levels directly correlate with all major clinical outcomes in FRDA, including not only cross-sectional markers such as AOO and disease severity, but also LoA as a disease milestone and long-term progression slopes of mFARS and USS. The associations were observed consistently across two independent cohorts and two distinct assay platforms, providing robust support for peripheral frataxin level as a clinically meaningful biomarker in both natural history studies and interventional trials.