Concurrent validity of single and groups of walking assessments following acute spinal cord injury.

STUDY DESIGN: Retrospective analysis of prospectively collected longitudinal data. Variables of interest are timed and untimed walking assessments (10MWT, 6MWT, TUG, WISCI, SCIM3a, SCIM3b) and lower extremities motor scores (LEMS) from both sides' lower limb motor segments, measured five times within the first year after acute spinal cord injury (SCI). OBJECTIVES: Assessing concurrent validity of single and groups of walking assessments in comparison with LEMS in SCI patients. SETTING: European Multicenter study about Spinal Cord Injury, a collaboration of 22 centers. METHODS: Canonical correlation analysis (CCA) was applied to single and groups of assessments at each time point, separately for patients able to perform timed walking assessments (less impaired; patient subgroup I) and for all patients (no selection; patient subgroup II). RESULTS: In patient subgroup I, SCIM3b, WISCI, 10MWT and 6MWT all had high and similar concurrent validity one year after injury. Among all groups of three walking assessments, SCIM3a, WISCI and 10MWT had highest concurrent validity, similar to all six walking assessments together. Timed walking assessments generally had higher concurrent validity than untimed ones. In patient subgroup II, WISCI distinctly had highest concurrent validity one year after injury, similar to all three untimed walking assessments together. CONCLUSIONS: CCA can assess concurrent validity of single and groups of assessments. Minimal sets of walking assessments with comparable concurrent validity as all assessments together were proposed. As these sets differ by patient group, walking assessments should be specified according to expected walking ability to allow for targeted, cost-effective application of assessments.

Challenges for defining minimal clinically important difference (MCID) after spinal cord injury.

STUDY DESIGN: This is a review article. OBJECTIVES: This study discusses the following: (1) concepts and constraints for the determination of minimal clinically important difference (MCID), (2) the contrasts between MCID and minimal detectable difference (MDD), (3) MCID within the different domains of International Classification of Functioning, disability and health, (4) the roles of clinical investigators and clinical participants in defining MCID and (5) the implementation of MCID in acute versus chronic spinal cord injury (SCI) studies. METHODS: The methods include narrative reviews of SCI outcomes, a 2-day meeting of the authors and statistical methods of analysis representing MDD. RESULTS: The data from SCI study outcomes are dependent on many elements, including the following: the level and severity of SCI, the heterogeneity within each study cohort, the therapeutic target, the nature of the therapy, any confounding influences or comorbidities, the assessment times relative to the date of injury, the outcome measurement instrument and the clinical end-point threshold used to determine a treatment effect. Even if statistically significant differences can be established, this finding does not guarantee that the experimental therapeutic provides a person living with SCI an improved capacity for functional independence and/or an increased quality of life. The MDD statistical concept describes the smallest real change in the specified outcome, beyond measurement error, and it should not be confused with the minimum threshold for demonstrating a clinical benefit or MCID. Unfortunately, MCID and MDD are not uncomplicated estimations; nevertheless, any MCID should exceed the expected MDD plus any probable spontaneous recovery. CONCLUSION: Estimation of an MCID for SCI remains elusive. In the interim, if the target of a therapeutic is the injured spinal cord, it is most desirable that any improvement in neurological status be correlated with a functional (meaningful) benefit.