Title

Item response theory methods can improve the measurement of physical function by combining the modified health assessment questionnaire and the SF-36 physical function scale

UMMS Affiliation

Department of Quantitative Health Sciences

Publication Date

3-6-2007

Document Type

Article

Subjects

*Activities of Daily Living; Adolescent; Adult; Aged; Aged, 80 and over; Antirheumatic Agents; Arthritis, Rheumatoid; Double-Blind Method; Female; Humans; Immunoconjugates; Male; Middle Aged; Psychometrics; *Quality of Life; Questionnaires; *Sickness Impact Profile

Disciplines

Biostatistics | Epidemiology | Health Services Research

Abstract

OBJECTIVE: To compare the measurement properties of the Modified Health Assessment Questionnaire [MHAQ], the SF-36((R)) Health Survey 10 item Physical Functioning scale [PF10], and scores from an item response theory (IRT) based scale combining the two measures.

STUDY DESIGN: Rheumatoid arthritis (RA) patients (n = 339) enrolled in a multi-center, randomized, double-blind, placebo-controlled trial completed the MHAQ and the SF-36 pre- and post-treatment. Psychometric analyses used confirmatory factor analysis and IRT models. Analyses of variance were used to assess sensitivity to changes in disease severity (defined by the American College of Rheumatism (ACR)) using change scores in MHAQ, PF10, and IRT scales. Analyses of covariance were used to assess treatment responsiveness.

RESULTS: For the entire score range, the 95% confidence interval around individual patient scores was smaller for the combined (total) IRT based scale than for other measures. The MHAQ and PF10 were about 70% and 50% as efficient as the total IRT score of physical functioning in discriminating among ACR groups, respectively. The MHAQ and PF10 were also less efficient than the total IRT score in discriminating among treatment groups.

CONCLUSIONS: Combining scales from the two short forms yields a more powerful tool with greater sensitivity to treatment response.

Rights and Permissions

Citation: Qual Life Res. 2007 May;16(4):647-60. Epub 2007 Mar 3. Link to article on publisher's site

Journal/Book/Conference Title

Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation

PubMed ID

17334829

Related Resources

Link to Article in PubMed