Quantifying the impact of upper limb tremor on the quality of life of people with multiple sclerosis: a comparison between the QUEST and MSIS-29 scales

Background: Upper limb tremor is common in people with multiple sclerosis (pwMS) and can affect day to day function, impacting on their tremor related quality of life (tremor-QOL). The Quality of Life in Essential Tremor Questionnaire (QUEST) is a tremor-QOL scale, however it has not been validated for use in pwMS. This is in contrast to the Multiple Sclerosis Impact Scale (MSIS-29), a MS health related QOL (MS-QOL) scale validated in pwMS. The aim of this study was to quantify tremor-QOL in pwMS using both the QUEST and MSIS-29 and establish the convergent validity of the QUEST scale with the MSIS-29. Methods: Data were derived from an existing registered clinical trial studying the efficacy of Botox (onabotulinumtoxinA) compared to placebo in pwMS-related upper limb tremor (ACTRN12617000379314). We determined MS-related disability (Expanded Disability status scale score (EDSS)), tremor severity (Bain and Findley Clinical Tremor Rating Scale (Bain)), cerebellar function (Scale for the Assessment and rating of Ataxia (SARA)), and upper limb manual dexterity (9 Hole Peg Test (9-HPT)). The QUEST and MSIS-29 were used to quantify tremor-QOL and MS-QOL respectively. Convergent validity was investigated by examining the correlation between QUEST and MSIS-29, and the pattern of correlation of the two scales compared to the EDSS, SARA, BAIN and 9-HPT. Results: Our cohort of 57 patients (16 male; 41 female), mean age of 47.6, had moderate MS-related disability with median EDSS score of 5 (IQR = 3.5). Median Bain score was 8, indicating mild tremor severity, which corresponded to mild to moderately poor tremor-QOL given mean Quest Summary Index (QSI) of 45.7. QSI correlated to tremor severity as measured by Bain total score (rs(55) = 0.339, p < 0.01), manual dexterity as measured by 9-HPT (rs(55) = 0.304, p < 0.05), and MS disease activity measured by EDSS (rs(55) = 0.347, p < 0.01). MSIS-29 also showed correlations to EDSS, and 9-HPT, but did not correlate to Bain total score. There was a strong relationship between QSI and MSIS-29 in pwMS (r(55) = 0.709, p < 0.01). Conclusion: In this cross-sectional study, we found that both the MS-QOL and tremor-QOL of pwMS with upper limb tremor was reduced. We were also the first to demonstrate that tremor-QOL in pwMS with upper limb tremor can be measured using the QUEST, which may be better suited for use in pwMS affected by arm-tremor than the MSIS-29. There is a lack of literature to specifically address tremor-QOL in pwMS, and more research is warranted.