VOLUME 46 | NUMBER 6 | DECEMBER 2011
Examining Multiple Sources of Differential Item Functioning on the Clinician & Group CAHPS® Survey
Keywords: Differential item functioning; racial and ethnic disparities; patientsâ€™ experiences of care; psychometrics; item response theory
Objective: To evaluate psychometric properties of a widely used patient experience survey.
Data Sources: English-language responses to the Clinician & Group Consumer Assessment of Healthcare Providers and Systems (CG-CAHPS®) survey (nÂ =Â 12,244) from a 2008 quality improvement initiative involving eight southern California medical groups.
Methods: We used an iterative hybrid ordinal logistic regression/item response theory differential item functioning (DIF) algorithm to identify items with DIF related to patient sociodemographic characteristics, duration of the physicianâ€“patient relationship, number of physician visits, and self-rated physical and mental health. We accounted for all sources of DIF and determined its cumulative impact.
Principal Findings: The upper end of the CG-CAHPSÂ® performance range is measured with low precision. With sensitive settings, some items were found to have DIF. However, overall DIF impact was negligible, as 0.14 percent of participants had salient DIF impact. Latinos who spoke predominantly English at home had the highest prevalence of salient DIF impact at 0.26 percent.
Conclusions: The CG-CAHPSÂ® functions similarly across commercially insured respondents from diverse backgrounds. Consequently, previously documented racial and ethnic group differences likely reflect true differences rather than measurement bias. The impact of low precision at the upper end of the scale should be clarified.
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