Objective: Develop and validate a TETRAS PRO subscale

Background: The Essential Tremor Rating Assessment Scale (TETRAS) is a popular scale for essential tremor (ET), but its activities of daily living (ADL) and performance (P) subscales are based on a structured interview and physical exam. No patient-reported outcome (PRO) scale for ET has been developed according to US regulatory guidelines.

Method: Fourteen items, rated 0-4, were derived from TETRAS ADL and structured cognitive interviews of 19 ET patients. Convergent validity analyses of TETRAS PRO versus TETRAS ADL, TETRAS-P, and the Quality of Life in Essential Tremor Questionnaire (QUEST) were computed for 67 adults with ET or ET plus. Test-retest reliability was computed at intervals of 1 and 30 days. The influence of mood (Hospital Anxiety and Depression Scale, HADS) and coping behaviors (Essen Coping Questionnaire, ECQ) was examined with multiple linear regression.

Results: TETRAS PRO was strongly correlated (r>0.7) with TETRAS ADL, TETRAS-P, and QUEST and exhibited good to excellent reliability (Cronbach alpha 95%CI=0.853-0.926; 30-day test-retest intraclass correlation 95%CI=0.814-0.921). The 1-day and 30-day estimates of minimum detectable change (MDC) were 7.2 and 6.6. TETRAS-P (r_semipartial=0.607), HADS depression (r_semipartial= 0.384), and the coping strategy of information seeking and exchange of experiences (r_semipartial=0.176) contributed statistically to TETRAS PRO in a multiple linear regression (R²=0.67).

Conclusion: TETRAS PRO is a valid and reliable scale that is influenced strongly by tremor severity, moderately by mood (depression), and minimally by coping skills. The MDC for TETRAS PRO is likely to be smaller than clinically important change.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/validation-of-a-new-patient-reported-outcome-scale-for-the-assessment-of-essential-tremor/