Minimal Clinically Important Difference in TETRAS Score for Essential Tremor

Minimum clinically important difference (MCID) helps distinguish clinically meaningful benefit from statistically significant, but clinically trivial, change. Modified versions of the Essential Tremor Rating Assessment Scale (TETRAS), including the modified activities of daily living (mADL) scale and the mADL11 scale, are frequently used as primary outcome measures in essential tremor (ET) clinical trials, but MCIDs for these measures have not been established. Here, we estimated MCIDs for the mADL and mADL11 scales in ET.

Data from the TRANQUIL multicenter, randomized controlled trial of an artificial intelligence-driven transcutaneous peripheral nerve stimulation device for ET were analyzed. Anchor-based approaches using the Clinical Global Impression of Improvement (CGI-I) and the Patient Global Impression of Improvement (PGI-I) were used as primary methods for MCID estimation. Mean changes in mADL and mADL11 were calculated for participants rated as "minimally improved" and "no change." Associations between anchor measures and score changes were assessed with Spearman's correlation coefficients. Receiver operating characteristic (ROC) analyses were performed to identify cutoff values that best distinguished minimal improvement from no change.

The anchor measures demonstrated acceptable correlations with changes in mADL and mADL11 scores. Estimated MCID values for mADL ranged from -3.5 to -6.2, and values for mADL11 ranged from -1.0 to -4.1 ROC-derived estimates produced the lowest thresholds, whereas PGI-I-based estimates yielded the highest. Our recommended MCID values, based on patient report, are -6.2 for mADL and -4.1 for mADL11.

This study establishes clinically meaningful change thresholds for two commonly used TETRAS-based outcome measures in ET. These MCIDs may aid interpretation of future clinical ET trials.