Cognitive Processing Speed Impairment Does Not Influence the Construct Validity of Six-Spot Step Test Performance in People With Multiple Sclerosis

The psychometric properties of the Six-Spot Step Test - a systematic review using the COSMIN guidelines

OBJECTIVE

Accurate and reliable balance measures are important for prescribing fall prevention treatments and monitoring their effectiveness. Thus, we aimed to systematically review the psychometric properties of the Six-Spot Step Test, an increasingly used measure of dynamic balance.

DATA SOURCES

A literature search using the free-text term "Six-Spot Step Test" was performed on 12 February 2024, in Medline, Embase, Rehabilitation & Sports Medicine and SPORTDiscus. Eligibility criteria were adults aged 18 or more, trials evaluating the psychometric properties of the Six-Spot Step Test, and English-language articles. Conference abstracts were excluded.

REVIEW METHODS

Two investigators screened and selected data independently and assessed the methodological quality and evidence using the COSMIN Risk of Bias checklist and modified GRADE approach. One investigator extracted study characteristics such as design, population and psychometric properties.

RESULTS

Of the 159 articles identified, 16, evaluating multiple measurement properties, were included in the final analysis. A total of 1319 people participated, including people affected by Stroke, multiple sclerosis, Parkison's disease, chronic inflammatory polyneuropathy and older adults with balance problems. Eight articles assessing reliability (n = 618, intraclass correlations coefficient ≥0.7, minimal detectable change = 22%) and 12 construct validity (n = 1082, 83% true hypothesis, area under the curve >0.7) exhibited sufficient methodological quality with high-level evidence, while two studies (n = 167) examining responsiveness showed very low evidence.

CONCLUSION

Apart from responsiveness, robust evidence supports the reliability and validity of the Six-Spot Step Test for assessing dynamic balance in a specific group of individuals with neurological diseases and older adults. Further, it is considered feasible for clinical use.

Criterion validity of muscle strain analyses of skeletal muscle function in patients with multiple sclerosis

BACKGROUND

Despite the wide range of existing performance measures to evaluate functional status of patients with multiple sclerosis, the heterogeneous nature of the disease hinders clinical characterization and monitoring of disease severity. Speckle tracking ultrasonography is a non-invasive technique to assess isolated muscle function by evaluating the contractile properties of muscle tissue, i.e. muscle strain. The aim of this study was to investigate whether muscle strain measured by speckle tracking ultrasonography could be a useful quantitative measure of muscle function in patients with multiple sclerosis. The criterion validity of muscle strain was compared to that of validated performance measures of upper and lower extremity function.

METHODS

This cross-sectional study used baseline data from an explorative observational cohort study (the MUST study). Participants recruited from a hospital outpatient MS clinic underwent speckle tracking ultrasonography of the biceps brachii, supraspinatus, and soleus muscles of the dominant side according to pre-defined submaximal isometric contractions. Participants also completed the Timed 25-Foot Walk Test, the Six Spot Step Test, the 2-minute walking test, the Nine-Hole Peg Test, the 12-item Multiple Sclerosis Walking Scale, and the Oxford Shoulder Score. Gaussian distribution was investigated by visual inspection of normal probability plots and the Shapiro-Wilk test. The Timed 25-Foot Walk Test and Nine-Hole Peg Test were selected as gold standards for function of the lower and upper extremities, respectively. Criterion validity was assessed using Spearman's rank-order correlation coefficient ρ (rho), comparing the muscle strain and performance measures against predefined gold standards. Differences in criterion validity were estimated using squared correlations on the Fischer's Z-scale, with non-parametric bootstrapping to obtain bias-corrected, accelerated bootstrap confidence intervals (95% BCa).

RESULTS

Criterion validity showed good to excellent correlations between the gold standard for lower extremity function and the 2-minute walking test and Six Spot Step Test, and a fair correlation to the 12-item Multiple Sclerosis Walking Scale. No significant correlation was found between the gold standard for upper extremity function and the performance measure. There were no significant correlations between the gold standards and muscle strain.

CONCLUSION

The absence of criterion validity for muscle strain alongside fair to strong criterion validity for the performance measures indicates that speckle tracking ultrasonography assessment of muscle strain is either invalid or evaluates other constructs of multiple sclerosis. Muscle strain assessed by speckle tracking ultrasonography cannot be recommended for the evaluation of treatment effects or disease progression in multiple sclerosis.