Designing and psychometric evaluation of disease-related fear scale (D-RFS) in adults with epilepsy: A sequential exploratory mixed methods design

Background: Disease-related fear is one of the important diagnoses of healthcare providers in caring for people with epilepsy whose conceptual dimensions should be discovered and investigated. To this end, it is necessary to provide healthcare providers with appropriate tools to assess fears related to the disease in accordance with the sociocultural milieu of each community.

Aim: The purpose of this study was to design and psychometrically evaluate the disease-related fear scale (D-RFS) in adults with epilepsy.

Methods: This study was of a sequential exploratory mixed methods design conducted in Iran in 2019. In the item generation phase, inductive (face-to-face, semi-structured interviews with 14 adult patients with epilepsy) and deductive (literature review) were used. In the item reduction, integration of qualitative and literature reviews and scale evaluation were performed. For the scale evaluation, face validity, content validity, construct validity [exploratory factor analysis (EFA) (n = 367) and confirmatory factor analysis (CFA) (n = 250)], and convergent and divergent validity and reliability (internal consistency and stability) were investigated.

Results: After the qualitative phase and literature review, 40 items were codified. After investigation of the qualitative and quantitative face validity, 7 items were deleted. Two items were deleted due to content validity ratio (CVR) of less than 0.56 and one item due to content validity index (CVI) of less than 0.78. Finally, a 30-item scale was obtained, and its construct validity was assessed. Kaiser-Meyer-Olkin (KMO) index was 0.85, and Bartlett's test of sphericity was 7237.504, P < 0. 001. The results of CFA showed that the bivariate model of the D-RFS (fear of seizure consequences and fear of the disease's long-term consequences) had the most appropriate fitness to the data. Convergent and divergent validity results showed that the values of composite reliability (CR) and average variance extracted (AVE) for the two factors were greater than 0.7 and 0.5, respectively, and the AVE for each factor was greater than CR. Internal consistency of the first and second factors were obtained 0.891 and 0.910, respectively. Cronbach's alpha coefficient for the total scale was obtained 0.921. The results of test-retest reliability showed that there was a significant agreement between the scores of the test and retest (P < .001).

Conclusion: The D-RFS has an acceptable factorial structure, and its internal consistency was confirmed by different approaches. This scale is a valid and reliable tool for assessing disease-related fear in patients with epilepsy. The simplicity of the items and the appropriate time to complete the scale can be considered as its strengths.