FXN and Friedreich ataxia: Comparison of FRDA patients versus controls/carriers, resulted in a 92.3 % sensitivity and a 96.9 % specificity for a cut-off value of frataxin of 0.35 pg/μg (p < 0.0001, area = 0.968), while comparison of FRDA patients/carriers with controls, resulted in a 92.1 % sensitivity and a 92.6 % specificity for a cut-off value of 1.19 pg/μg (p < 0.0001, area = 0.968).