The Essential Tremor Rating Assessment Scale (TETRAS)
A two-subscale tremor rating instrument developed by the Tremor Research Group.
By Claire White
- Performance subscale. 9 items rated by a clinician, each 0 to 4 in half-point steps, total 0 to 64.
- Activities of daily living subscale. 12 items collected by interview, each 0 to 4, total 0 to 48.
- Lower scores mean less tremor on both subscales.
- Developed by the Tremor Research Group and first published in 2008. Recommended by the Movement Disorder Society tremor task force.
Psychometrics
Intraclass correlations from Elble et al. (2012), from 10 specialists rating 50 videos twice. Higher is better.
What does the TETRAS measure?
Tremor severity, from two directions. The performance subscale is an examination. A clinician rates head tremor, face tremor, voice tremor, upper limb postural and kinetic tremor, lower limb tremor, spiral drawing, handwriting, dot approximation, and standing, each from 0 to 4 in half-point steps. Item 4, upper limb tremor, is the sum of three manoeuvres for each arm, so it alone runs from 0 to 24 and dominates the total.
The daily living subscale is an interview. It covers speaking, feeding, drinking, hygiene, dressing, pouring, carrying objects, using keys, writing, working, social impact, and the one activity affected by tremor that matters most to the person being assessed.
| Subscale | Collected by | Items | Range |
|---|---|---|---|
| Performance | Clinician examination | 9 | 0 to 64 |
| Activities of daily living | Clinician interview | 12 | 0 to 48 |
What does a TETRAS score mean?
Lower means less tremor on both subscales, and the two are reported separately rather than summed. The performance subscale is the usual outcome measure in trials of tremor-suppressing treatments, because it is the one an examiner can standardise. The daily living subscale answers a different question, which is whether any of that translates into an easier day.
The literature publishes no agreed severity bands for the TETRAS, so there is no table of mild, moderate, and severe here. A score is read against the same person’s earlier scores. What is published is how much movement counts as real. On the performance subscale the minimum detectable change is 8.9%, so smaller movements than that sit inside the measurement noise.
One limit is worth stating plainly. Agreement between raters is not even across the body. Head and upper limb ratings agree closely, at intraclass correlations of 0.86 to 0.96, while voice, face, trunk, and leg ratings agree less well. A change confined to one of those weaker regions deserves more caution than the same change in an arm. Results are reference information for the care team, not a diagnosis.
How the TETRAS is administered
- Administered by
- A clinician. The performance subscale is an examination, the daily-living subscale an interview.
- Equipment
- Pen and paper, including a spiral and a handwriting sample
- Rating steps
- Performance items are rated in half-point steps, daily-living items in whole points
- Age range
- Adults
Which conditions is the TETRAS used for?
Related instruments
- MDS-UPDRS Part IIIHow tremor is rated inside the Parkinson's motor examination, when the diagnosis is Parkinson's rather than essential tremor
- MDS-UPDRSThe full Parkinson's rating scale, across motor and non-motor domains
- EQ-5DGeneric health-related quality of life, reported alongside TETRAS scores in essential tremor research
TETRAS questions, answered
How is the TETRAS scored?
As two separate subscales that are not added together. The performance subscale has 9 items, each rated 0 to 4 in half-point steps, and totals 0 to 64. Item 4, upper limb tremor, carries most of that range on its own, because it is the sum of three manoeuvres for each arm and so runs 0 to 24. The daily-living subscale has 12 items, each rated 0 to 4 in whole points, and totals 0 to 48. Lower is better on both.
What is a normal TETRAS score?
0 on both subscales means no tremor observed and no reported effect on daily life. Beyond that there are no published severity bands for the TETRAS, so a score is read against the same person's earlier scores rather than against a cutoff. On the performance subscale, a change of about 9% is the smallest that can be reliably distinguished from measurement noise.
What does the TETRAS performance subscale examine?
Nine things, in this order. Head tremor, face tremor, voice tremor, upper limb postural and kinetic tremor, lower limb tremor, spiral drawing, handwriting, dot approximation, and standing. The reliability of those items is not uniform. Head and upper limb ratings agree closely between raters, while voice, face, trunk, and leg ratings agree less well, which matters when a small change in one of those regions is being used to judge a treatment.
What does the TETRAS daily living subscale cover?
Twelve activities, collected by interview rather than filled in alone. They cover speaking, feeding, drinking, hygiene, dressing, pouring, carrying objects, using keys, writing, working, social impact, and the activity affected by tremor that matters most to the person. That last item is what lets the subscale follow what an individual actually cares about rather than a fixed list.
Who can administer the TETRAS?
A clinician. The performance subscale is a physical examination with standardised tasks, and the daily-living subscale is an interview the clinician conducts and scores. Neither is designed to be completed alone.
Is the TETRAS used for Parkinson's disease?
It was built for essential tremor, and that is what the Movement Disorder Society tremor task force recommends it for. Essential tremor is a separate condition from Parkinson's disease, and Parkinson's tremor is rated inside the MDS-UPDRS motor examination instead. The two conditions are often confused with each other, which is the usual reason people arrive at both scales at once.
Evidence, psychometrics and provenance
Developed by the Tremor Research Group and first published in 2008. Its reliability was established in 2012 by Elble and colleagues, who filmed 44 people with essential tremor and 6 controls and had 10 specialists rate every video twice, 1 to 2 months apart. The Movement Disorder Society tremor task force reviewed the field the following year and put the TETRAS among the eight instruments it recommends.
- Weaker regions
- Voice, face, trunk, and leg tremor were rated less consistently than head and upper limb (Elble et al., 2012)
- Minimum detectable change
- 8.9% on the performance subscale (Voller et al., 2014)
- Sensitivity to change
- Effect size d 4.75 under an alcohol challenge in 15 adults (Voller et al., 2014)
- Task force status
- Recommended for essential tremor by the Movement Disorder Society tremor task force (Elble et al., 2013)
References
- 1.Elble R, Comella C, Fahn S, et al. Reliability of a new scale for essential tremor. Mov Disord. 2012;27(12):1567-1569.
- 2.Elble R, Bain P, Forjaz MJ, et al. Task force report: scales for screening and evaluating tremor: critique and recommendations. Mov Disord. 2013;28(13):1793-1800.
- 3.Voller B, Lines E, McCrossin G, et al. Alcohol challenge and sensitivity to change of the Essential Tremor Rating Assessment Scale. Mov Disord. 2014;29(4):555-558.
- 4.Gerbasi ME, Elble RJ, Jones E, et al. Associations among tremor amplitude, activities of daily living, and quality of life in patients with essential tremor. Tremor Other Hyperkinet Mov (N Y). 2024;14:22. (Source for the performance and daily-living item lists and score ranges.)
- 5.Shih LC, Stevenson MT, Bellows S, et al. Validation of a new patient-reported outcome measure of the functional impact of essential tremor on activities of daily living. Tremor Other Hyperkinet Mov (N Y). 2024;14:26. (Source for the daily-living subscale content and its interview format.)
This assessment uses a validated instrument and is reference information, not a diagnosis.