Validation study of the Spanish version of the Fahn-Tolosa-Marín scale for essential tremor
Introduction. The Fahn-Tolosa-Marín (FTM) tremor rating scale has been widely used in clinics for the estimation of tremor severity. However, a Spanish language version of this scale has still not been formally validated.
Aim. To provide support to the validity and reliability of this version of FTM Scale.
Patients and methods. A cross-sectional study was conducted on essential tremor patients. Severity was rated using the FTM scale. Upper limb disability was evaluated by terms of Disabilities of the Arm, Shoulder and Hand Scale (DASH), and to health-related quality of life using the Short Form-36 Health Survey (SF-36). Statistical analysis included sample description, reliability (Cronbach’s alpha), convergent validity, and discrimination capacity tests (ROC curves).
Results. Forty patients with essential tremor (22 women, 18 men) were included, with a mean age of 65.8 ± 14.7 years (range: 21-90 years). Internal consistency of the FTM was high: Cronbach’s alpha: 0,90 (subscale A: 0.85; subscale B: 0.91; subscale C: 0.77), and the floor and ceiling effects were negligible. The FTM (subscale C) showed high correlations with DASH, and acceptable diagnostic capacity, with an area under the curve of 0.86 (95% CI: 0.67-1.00), sensitivity 78% and specificity 75% for a cut-off score > 5.5.
Conclusion. The Spanish version of FTM the rating scale is a reliable and valid tool to evaluate disability in patients with essential tremor, and a suitable instrument for use in medical research, as well as in clinical practice.
Key words. Clinimetric analysis. Disability. Essential tremor. Fahn-Tolosa-Marín scale. Outcomes. Rating scales. Tremor.