Investigating potential gender-based differential item functioning for items in the Kansas City Cardiomyopathy Questionnaire (KCCQ) Physical Limitations domain

Background: Women with heart failure report worse health-related quality of life, on average, than men. Whether this is due to true differences in care or that women and men interpret and respond to survey questions differently is unknown. In this study, we investigate potential gender-based differential item functioning (DIF) on the Kansas City Cardiomyopathy Questionnaire (KCCQ) Physical Limitations (PL) domain.Methods: Using data from Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION), a multicenter, randomized controlled trial of exercise training in patients with chronic heart failure with reduced ejection fraction (1670 men, 661 women), we assessed gender DIF using item response theory (IRT)–based Wald test and ordinal logistic regression. Both methods evaluated how men and women responded to each KCCQ item after adjusting for their physical limitation status.Results: A 5-item version of the KCCQ PL domain was evaluated to satisfy statistical assumptions of DIF methodology. No KCCQ items exhibited statistically significant DIF using the IRT-based Wald method, and two items exhibited DIF using the ordinal logistic regression method (KCCQ1e: Climbing a flight of stairs without stopping; KCCQ1f: Hurrying or jogging) (pConclusions: To accurately measure patient-reported outcomes, it is important to evaluate potential biases that may influence the ability to compare patient subgroups. The magnitude of DIF on the 5-item KCCQ PL domain was negligible.