Authors' objectives:

To develop a patient-based, disease-specific measure of the health impact of multiple sclerosis (MS) that is clinically useful, and scientifically sound, and suitable for use as an outcome measure in clinical trials and in routine clinical practice.

Authors' results and conclusions: - Stage 1: a pool of 129 items was generated. - Stage 2: the item pool was reduced to a 29-item measure of the physical (20 items) and psychological (nine items) impact of MS: the MSIS-29. - Stage 3: the MSIS-29 satisfied all recommended psychometric criteria for rigorous measurement. Data quality was excellent: missing data were low (maximum 3.9%), item test-retest reliability was high (r = 0.650.90) and scale scores could be generated for >98% of respondents. Item descriptive statistics, item convergent and discriminant validity, and factor analysis supported summing items to produce two summary scores. MSIS-29 physical and psychological scale scores showed good variability, low floor and ceiling effects, good internal consistency (Cronbach's a >= 0.91) and test-retest reliability (intraclass correlation >= 0.87). Correlations with other measures, and confirmation of hypotheses about group differences, provided evidence for the validity of the MSIS-29 as a measure of the physical and psychological impact of multiple sclerosis. Effect sizes (physical scale = 0.82, psychological scale = 0.66) provided preliminary evidence for responsiveness.

Authors' recommendations: The 29-item MSIS-29 is a rigorous new measure of the physical and psychological impact of MS. All psychometric criteria were satisfied and there is preliminary evidence of responsiveness. The MSIS-29 is particularly appropriate for use in clinical trials to evaluate therapeutic effectiveness from the patients perspective. A limitation of the study is that the MS Society membership database was used to define the sampling frame; the percentage of people in the database with a neurologist-confirmed diagnosis of clinically definite MS, the disease type of those with MS and the representativeness of people who join charitable groups are unknown. Critical evaluations of the MSIS-29 completed by people with neurologist-confirmed MS in different settings will identify its strengths and weaknesses, and further define its role in clinical practice and research. Head-to-head comparisons of the psychometric properties of the MSIS-29 and other outcome measures for MS will help to determine the relative advantages of different instruments so that the choice of measures for studies can be evidence based.

Authors' methods: Outcome measure development

Project Status: Completed

URL for project: http://www.hta.ac.uk/997

Year Published: 2004

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: England, United Kingdom

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk

Copyright: 2009 Queen's Printer and Controller of HMSO