Development and Psychometric Assessment of a Measurement Instrument for Functioning and Function-Affecting Factors in Women With Breast Cancer: A Rasch Analysis Approach
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Published on: April 23, 2014
Farkhondeh Jamshidihosseinabadi1, Maryam Farzad2,3, Enayatollah Bakhshi4
1Department of Occupational Therapy, School of Allied Medical Sciences, Zanjan University of Medical Sciences, Zanjan, Iran.
Purpose:
To develop and psychometrically evaluate an instrument for assessing functioning and function-affecting factors in women with breast cancer, based on the International Classification of Functioning, Disability and Health (ICF) Core Set for Breast Cancer.
Methods:
This methodological study combined a systematic literature review, qualitative interviews with women with breast cancer, and expert consultation to develop the questionnaire. Face validity was assessed in 10 women with breast cancer, content validity by 10 experts, and structural validity and reliability in 305 women with breast cancer. Rasch analysis was performed using dichotomized item responses, and confirmatory factor analysis (CFA) was conducted in R using the WLSMV estimator for ordered categorical variables. Internal consistency was evaluated using McDonald's Omega.
Results:
Following content validation, the preliminary questionnaire contained 70 items (40 functioning and 30 function-affecting factors). Rasch analysis identified misfitting items and resulted in a final 55-item instrument comprising 32 functioning items and 23 function-affecting items. CFA supported the proposed multidimensional structure after theoretically justified model refinement. The functioning section demonstrated satisfactory model fit (CFI = 0.976, TLI = 0.974, RMSEA = 0.040, 90% CI = 0.034-0.046), while the function-affecting factors section also demonstrated acceptable fit (CFI = 0.979, TLI = 0.977, RMSEA = 0.054, 90% CI = 0.046-0.062). Although several items showed relatively low standardized factor loadings, they were retained because of acceptable Rasch fit, satisfactory content validity, and conceptual importance. McDonald's Omega indicated acceptable internal consistency across the retained subscales.
Conclusion:
The findings provide preliminary evidence supporting the reliability and structural validity of this ICF-based instrument for assessing functioning and function-affecting factors in women with breast cancer. Further validation in independent populations is recommended before broader clinical implementation.
