Participants and procedures
The UW-CSS and UW-CBS were translated into four languages using forward and backward translation with reconciliation. Semi-structured cognitive interviews (CIs) with caregivers were used to evaluate translated versions. Data collected in a large-scale administration were used to evaluate differential item functioning (DIF) and compare stress and benefit scores between European Union (EU) countries and the USA.
Translations
The UW-CSS and UW-CBS translations were conducted by The Academy of Languages Translation and Interpretation Services (AOLTI, https://aolti.com/) who specialize in medical translations. All language translations were back-translated to English by AOLTI. Trained native speakers of each language worked with the AOLTI to arrive at the final translations to be tested in CIs.
Cognitive interviews
Trained native speaker interviewers completed semi-structured CIs [3] over the phone or via web teleconference software (e.g., Zoom) with caregivers of children (< 18 years) with epileptic encephalopathies (EE). Interviews were recorded and the interviewers’ notes were used to compile summaries of feedback on each item. Caregivers were defined as a parent or legal guardian who coordinates and provides most of the unpaid day-to-day care for a child. Eligibility criteria included residing in France, Germany, Italy, or Spain, and ability to read, speak and understand French, German, Italian, or Spanish, respectively. Participants were recruited with help from clinicians who see patients with EE and from participants in previous studies [4]. A minimum of five caregivers reviewed each item in each language, with at least one male and two caregivers of younger children with EE (< 9 years). The interviews assessed the comprehension, clarity, and cultural applicability of the items. Items that required significant modifications after CI testing were tested in a second round of interviews with at least three participants. Two additional German caregivers of healthy children were recruited due to difficulties translating the term “caregiving” into German. Caregivers also completed a short online survey with demographic and clinical information. Surveys were administered through the REDCap (Research Electronic Data Capture) web-based software platform [5, 6]. Participants provided informed consent and were sent a €43 electronic gift card.
Large scale administration
The final translated and revised UW-CSS and UW-CBS items were administered to a larger sample (N = 400 target sample size) along with demographic and child health questions via an online survey also using REDCap [5, 6]. Adult caregivers (> 18 years) residing in France, Italy, Germany, or Spain and fluent in the native language of the country, and caring for at least one child under age 18 years were eligible. At least 100 caregivers per country was targeted, with additional subsample targets per country: 50 caregivers of a child with EE, 25 caregivers of a child with a chronic health condition, and 25 caregivers of children with no health conditions. Caregivers were recruited from the CI study and by Op4G (https://op4g.com/), a market research organization. Participants recruited by Op4g were not paid but participants recruited from the CI study were sent an €23 electronic gift card after completing the survey.
Analyses
Cognitive interviews
Any problematic or confusing items were flagged and addressed. Minor changes were made to the English version to keep content and constructs as consistent as possible across all versions.
Differential item function
DIF analyses were conducted using data from the large-scale administration to examine the linguistic and cultural equivalence of the translations. The original US development sample, described in detail in Amtmann et al. [1] was used as a comparison for the analyses. The US development sample included a mix of caregivers of children with EE, Down syndrome, muscular dystrophy, or children with no specific health care needs. Prior to running DIF analyses unidimensionality of the scales was examined using 1-factor confirmatory factor analysis (CFA) using Mplus software 8.2. [7]. A comparative fit index (CFI) of 0.90 or higher was considered sufficient support for unidimensionality [8]. DIF was assessed by each country individually (e.g., US vs Spain) as well as by the combined sample (i.e., US vs EU) using the program lordif [9] in R [10] with an R2 criterion of 0.02, as is recommended for translation validity analyses [11]. If statistically significant DIF was observed DIF adjusted scores were calculated and compared to non-adjusted scores to determine the scale-level impact of DIF [12].
US and EU comparisons
Sample demographics were compared using Student’s t-tests or chi-squared tests. UW-CSS and UW-CBS 6-item short form scores were generated and summarized across countries and subgroups. Using the Student’s t-test, stress and benefit scores in EU countries were also compared to scores in the US sample utilized for the DIF analyses.
Short Forms
Fixed length short forms developed by Amtmann et al. [1] were revised based on the results of the CIs and DIF analyses. Items that were identified as problematic were removed and\or replaced with better functioning items and items without DIF. Internal consistency of the new short forms was examined using Chronbach’s alpha [13] and item convergent validity by calculating corrected item-total score correlations. Alpha values between 0.7 and 0.9 and correlations > 0.40 were considered acceptable [14].