Circular Timed Up and Go (cTUG) test for assessing balance among individuals with cerebellar ataxia: Development and validation.

Background: The cTUG is a modified version of conventional TUG. cTUG is an equilibrium test that challenges subjects’ ability to maintain balance in
response to the constant change in direction of walking.
Purpose: To develop and test the feasibility, reliability and validity of the Circular Timed Up and Go (cTUG) in assessing balance among individuals with
cerebellar ataxia (CA) and age-matched healthy individuals.
Methods: All the included participants were subject to three consecutive assessments within 2 days involving two independent assessors. The healthy
participants were subject to the cTUG and conventional Timed Up and Go (TUG) test. The participants with CA were subject to balance assessment using the
cTUG, conventional TUG, Berg Balance Scale (BBS), Limit of Stability (LOS) and Sensory Organization test (SOT), disease severity was assessed using the
Scale for the Assessment and Rating of Ataxia (SARA) and the quality of life was assessed using the EuroQol-5D-5L (EQ-5D-5L) Questionnaire. Reliability and
validity of cTUG were assessed. Intra-rater and inter-rater reliability were estimated by using the interclass correlation coefficient (ICC), values < 0.5 were
interpreted as poor, 0.5-0.75 as moderate, 0.75-0.9 as good and > 0.9 as excellent. Convergent, concurrent and external validity were assessed using the
Spearman correlation coefficient. Coefficient of 0.35-0.49 was interpreted as weak, 0.5-0.79 as moderate and > 0.8 as strong. Discriminant validity was
measured by the independent t-test, with p-value < 0.05 indicating a significance difference.
Results: The mean score of cTUG among healthy participants was 10 seconds while that among participants with CA was 52.64 seconds. The intra-rater and
intra-rater reliability of the cTUG was found to be strong among both healthy participants (ICC range, 0.961-0.977) and participants with CA (ICC range,
0.901-0.946). The correlation between cTUG and BBS (ρS=-0.613), SARA-BAL (ρS=0.408), SOT (ρS range, -0.607 to -0.214) and LOS (ρS range, -0.893 to
0.679) ranged from weak to moderate, indicating a poor to moderate convergent validity. The correlation between cTUG and SARA (ρS=-0.179) was weak,
indicating poor concurrent validity. The correlation between cTUG and EQ-5D-5L (ρS=-0.847) is strong, indicating a good external validity. There is no
significant difference between the cTUG performance of frequent fallers and non-frequent fallers (p=0.791), indicating poor discriminant validity.
Conclusion(s): The cTUG is feasible and safe for assessing balance among people with CA. The reliability was found to be strong and the validity was weak
to strong. A future study recruiting a minimum of 30 ambulant people with CA with diverse underlying causes (sporadic, degenerative, and acquired) is
needed to consolidate these findings.
Implications: Balance assessment using the cTUG may be a better choice of assessment when compared to the conventional TUG among people with
cerebellar ataxia