Index of Overall Disability due to Multiple Sclerosis
Satyendra Nath Chakrabartty*
Indian Ports Association, India
*Corresponding Author: Satyendra Nath Chakrabartty, Indian Ports Association, India.
May 05, 2023; Published: June 03, 2023
Background: Existing tests to assess disabilities due to functional deficits in Multiple sclerosis (MS) differ in number of items, number of response-categories, domains covered, scoring systems, etc. and are not comparable.
Objective: The paper proposes two methods to convert discrete raw scores of items/domains of MS tests to continuous scores following normal distribution satisfying desired properties and facilitating meaningful comparisons, assessment of progress/deterioration, parametric statistical analysis and symmetric equivalent-scores for better comparisons and integration of MS tests.
Methods: Ordinal raw scores are converted to equidistant scores by weighted sum followed by linear transformations (Method 1) and alternate method of scoring health-state-profiles in 5-Domain 5-Level set up (Method 2). Proposed equivalent-scores having equal areas under normal curve help to derive meaningful cut-off scores, equivalent boundary points of the classes and integration of MS tests
Results: Proposed scores under each method help in computation of total score reflecting total disorder by overall index of disability in MS, with the same score range of items satisfy desired properties of measurement including meaningful arithmetic aggregations, minimization of tied scores. Domain scores and test scores follow normal and facilitate better ranking, comparisons, quantify changes from longitudinal data, and parametric statistical analysis, computation of reliability, validity, etc. Symmetric equivalent scores avoid conversion tables generated from the Crosswalk Studies which may vary by several points and may not provide inverse function for each score. The Method 2 indicates domain-wise status of a patient and helps practitioners to decide priorities and course of action accordingly. However, Method 2 requires significant modifications of existing tests to fit 5D-5L set up.
Conclusions: Considering theoretical advantages including meaningfulness of operations, easy comprehension, better comparisons, Method 1 is recommended with the suggestion to report test score and also domain scores.
Keywords: Multiple Sclerosis, Cognitive Tests; Normal Distribution; Equivalent Scores; Reliability; Responsiveness
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