Reliability, construct validity and measurement potential of the ICF comprehensive core set for osteoarthritis

Abstract

BackgroundThis study aimed to investigate the reliability and construct validity of the International Classification of Functioning, Disability and Health (ICF) Comprehensive Core Set for osteoarthritis (OA) in order to test its possible use as a measuring tool for functioning.Methods100 patients with OA (84 F, 16 M; mean age 63 yr) completed forms including demographic and clinical information besides the Short Form (36) Health Survey (SF-36®) and the Western Ontario and McMaster Universities Index of Osteoarthritis (WOMAC). The ICF Comprehensive Core Set for OA was filled by health professionals. The internal construct validities of "Body Functions-Body structures" (BF-BS), "Activity" (A), "Participation" (P) and "Environmental Factors" (EF) domains were tested by Rasch analysis and reliability by internal consistency and person separation index (PSI). External construct validity was evaluated by correlating the Rasch transformed scores with SF-36 and WOMAC.ResultsIn each scale, some items showing disordered thresholds were rescored, testlets were created to overcome the problem of local dependency and items that did not fit to the Rasch model were deleted. The internal construct validity of the four scales (BF-BS 16 items, A 8 items, P 7 items, EF 13 items) were good [mean item fit (SD) 0.138 (0.921), 0.216 (1.237), 0.759 (0.986) and -0.079 (2.200); person item fit (SD) -0.147 (0.652), -0.241 (0.894), -0.310 (1.187) and -0.491 (1.173) respectively], indicating a single underlying construct for each scale. The scales were free of differential item functioning (DIF) for age, gender, years of education and duration of disease. Reliabilities of the BF-BS, A, P, and EF scales were good with Cronbach's alphas of 0.79, 0.86, 0.88, and 0.83 and PSI's of 0.76, 0.86, 0.87, and 0.71, respectively. Rasch scores of BF-BS, A, and P showed moderate correlations with SF-36 and WOMAC scores where the EF had significant but weak correlations only with SF36-Social Functioning and SF36-Mental Health.ConclusionSince the four different scales derived from BF-BS, A, P, and EF components of the ICF core set for OA were shown to be valid and reliable through a combination of Rasch analysis and classical psychometric methods, these might be used as clinical assessment tools.

Validation and reliability of the Cardiff Visual Ability Questionnaire for Children using Rasch analysis in a Turkish population

“…According to another opinion, the sample size should be between 100–200 in the validation studies 13 14. So the sample size was set at 150 which was six times the number of 25 items.…”

“…The assumption of local independence is tested by performing a principle component analysis (PCA) of the residuals. A significant difference would be expected to occur by chance in 5% of the cases 3 14 15…”

“…Targeting of item difficulty to the person ability level can be evaluated with the person-item threshold distribution map which shows logarithmically transformed person and item locations on the same continuum along the x-axis 14 19…”

“…Items are also checked for differential item functioning (DIF) to determine whether, despite having equal levels of the underlying trait, different groups within a sample behave in a different manner for an individual item 14 19…”

The inter-rater reliability of the International Classification of Functioning, Disability and Health set for spinal cord injury nursing

“…The environmental factors have nine responses levels from − 4 (complete barrier) to + 4 (complete facilitator). Rasch analysis has been recommended for examining the fit, threshold estimates, local dependencies, unidimensionality, differential item functioning, and person separation indexes of the ICF-based assessment tools (Kurtais et al, 2011;Alviar et al, 2012;Bostan et al, 2012;Roe et al, 2013). Other psychometric properties such as criterion-related validity, internal consistency, inter-rater reliability and test-retest reliability can be examined using the classical test theory.…”