Differential item functioning of the CAHPS® In-Center Hemodialysis Survey

End-stage renal disease patients' experience of care is an integral part of the assessment of the quality of the care provided at hemodialysis centers and is needed to promote patient choice, quality improvement, and accountability. The purpose of this study is to evaluate the In-Center Hemodialysis Consumer Assessment of Healthcare Providers and Systems (ICH-CAHPS®) survey and its equivalence in different age, gender, race, and education subgroups.

The ICH-CAHPS survey was administered to 1454 patients from 32 dialysis facilities. For the characteristics compared, the sample had 756 participants younger than 65 years old, 739 men, 516 Black, 567 White, and 970 with less than high school diploma. Three different patient experience constructs were studied including nephrologist's communication and caring, quality of care and operations, and providing information to patients. We used item response theory analysis to examine the possibility of differential item functioning (DIF) by patient age, gender, race, and education separately after controlling for the other DIF characteristics and additional confounding variables including survey mode, mental, and general health status as well as duration on dialysis.

The three constructs studied were unidimensional and no major DIF was observed on the composites. Some non-equivalences were observed when confounders were not controlled for, suggesting that such covariates can be important factors in understanding the possibility of disparity in patients' experience.

The ICH-CAHPS is a promising survey to elicit hemodialysis patients' experience that has good psychometric properties and provides a standardized tool for assessing age, gender, race, or education disparity.