Quantitative phase.

Before the recruitment begins, the principal investigator will present the project to the paediatric service of the Arnau de Vilanova University Hospital of Lleida (HUAV). During medical consultations, the paediatric service will inform eligible participants about the study. If the caregiver agrees to participate, they will give consent for the paediatric service to share their contact details with the research team. The investigators will then contact the participant to explain the project in detail, schedule a first meeting to sign the Informed Consent, and complete the initial questionnaires. Additionally, participants who sign the informed consent will be asked to provide their contact information for potential follow-up regarding the qualitative interview.

In the first meeting, participants who meet the inclusion criteria and have signed the informed consent will be directed to a study homepage hosted on the university’s website. This website will provide a link to a secure platform specifically designed for collecting research data (PedsQL-FIM, ZBI, PSS-14).

Sociodemographic data.

Participants’ sociodemographic data will include descriptive information such as age, sex, household income, among others.

Inclusion criteria.

1. - >18 years old
2. - Being a caregiver of a child with Cerebral Palsy
3. - Spanish/Catalan speaking
4. - Willing to talk about their experiences and be audio/video-recorded.
5. - Accept and sign the informed consent form

Qualitative phase.

The interview guide will be refined based on the results of the quantitative phase. Additionally, the findings from the quantitative questionnaires will inform the selection of participants for the interview phase. The interview will take place in the Faculty of Nursing and Physiotherapy of the University of Lleida. Interviews will be conducted in either Spanish or Catalan (participants’ choice) and will be recorded in audio or video, with participants’ previous consent. Once all questionnaire data has been analysed, a subgroup will be created based on the results obtained, which will be related to the categories identified in the PedsQL™ Family Impact Module [15] and the Zarit Burden Interview [16], both in their Spanish versions.

Sample size considerations.

The quantitative sample size was estimated using GRANMO (estimation of a population mean). Assuming a 95% confidence level, a standard deviation of 21, based on Spanish normative data for the PedsQL-Family Impact Module [17]. Assuming an accessible finite hospital population of approximately 40 eligible caregivers and a precision of ±5 points on the 0–100 scale; the required sample is n = 26 completers. Allowing for an anticipated 15% attrition rate, the recruitment target is approximately 31 caregivers. This sample ensures estimation of the mean PedsQL-FIM score with adequate precision for the finite population. In addition, with n = 25–30 completers, two-tailed tests at α = 0.05 will have approximately 80% power to detect correlations of r = 0.50–0.54, providing sufficient power for moderate-to-large associations while acknowledging that smaller effects may be underpowered

Study status and timeline.

At the time of manuscript submission, the study has not yet started. The start date of the recruitment period for this study is expected to begin 02/06/2025 and expected to be completed by end of June 2025. Data collection is anticipated to be finalized by August 2025, and preliminary results are expected to be available by September 2025. This timeline is subject to minor adjustments depending on recruitment rates and operational logistics S1 Fig (Fig 1.)

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Fig 1. Participant timeline: Schedule of enrollment, interventions and assesments.

PSS-14: Perceived Stress Scale, PedsQL-FIM: Qualoty of Life by PedsQL^TM Family Impact Module, ZBI: Zarit Burden Interview.

https://doi.org/10.1371/journal.pone.0342763.g001

Perceived Stress Scale (PSS-14).

The PSS-14 is short and easy adaptation of the original Perceived Stress Scale (PSS), with the original author being Cohen, S. The European Spanish adaptation was conducted by Remor, E. [18].

The PSS measures the degree to which individuals perceive life situations as stressful over the past month, focusing on subjective control over unpredictable events and the distress associated with perceived lack of control. The PSS is more closely related to subjective evaluations of life events than objective measures of stressors [19]. The 14-item European Spanish version of the Perceived Stress Scale (PSS-14) will be employed to assess caregivers’ levels of perceived stress. This instrument comprises 14 items, each rated on a five-point Likert scale ranging from 0 to 4 (0 = never, 1 = rarely, 2 = sometimes, 3 = usually, 4 = almost always), yielding a total score between 0 and 56. Higher scores indicate greater perceived stress. The European Spanish adaptation of the PSS-14 has demonstrated acceptable psychometric properties, including good internal consistency (Cronbach’s alpha = .81), satisfactory test-retest reliability (r = .73), and evidence of concurrent validity and sensitivity [20].

Quality of Life by PedsQL™ Family Impact Module (PedsQL-FIM).

To assess the impact of paediatric chronic health conditions on caregivers and the family, the Spanish version of the PedsQL™ Family Impact Module will be used [15,21]. This module employs a multidimensional parent self-report to evaluate physical, emotional, social, and cognitive functioning, as well as communication and worry. The module can be completed within 5–10 minutes [21,22] The Pediatric Quality of Life Inventory Family Impact Module (PedsQL-FIM) will be utilized to evaluate the impact of paediatric health conditions on caregiver and family functioning. This instrument consists of 36 items, demonstrating excellent internal consistency reliability (Cronbach’s α = 0.97) (21). It measures eight core dimensions: physical functioning (6 items), emotional functioning (5 items), social functioning (4 items), cognitive functioning (4 items), communication (3 items), worry (5 items), daily activities (3 items), and family relationships (5 items). Responses are rated on a 5-point Likert scale (0 = never a problem to 4 = almost always a problem), then reverse scored and linearly transformed to a 0–100 scale (0 = 100, 1 = 75, 2 = 50, 3 = 25, 4 = 0), with higher scores indicating better perceived functioning. The total score is calculated by summing all item scores and dividing by the number of items completed [23].

Zarit Burden Interview (ZBI).

The Zarit Burden Interview is a widely used self-report instrument for measuring caregiver burden. ZBI assesses caregivers´ perceptions of burden that may inadvertently affect their health, personal, social or financial wellbeing [16].

Caregivers are requested to assess the level of burden they experience while caring for a loved one. Burden is defined as the degree to which a caregiver perceives negative effects on their emotional and physical health, social life, and finances, which may hinder their ability to provide care. Responses vary from “not at all” to “extremely.” It consists of 22 items, with the total score calculated by summing the scores of all the indicated items. It is suggested that a score from 0 to 21 means no to mild burden, 21–40 indicates mild to moderate burden, 41–60 indicates moderate to severe burden, and more than 61 means severe burden [24].

The Spanish version developed by Martin-Carrasco et al. [25] showed a good internal reliability (Cronbach alpha coefficient of 0.92) [17,26].

Quantitative data.

The quantitative data will be analysed using descriptive statistics and frequency counts. Sociodemographic characteristics will be described. Descriptive statistics will be reported with means and standard deviations for continuous variables with normal distribution (age, child’s age, PSS-14, PedsQL-FIM, ZBI), or medians and interquartile ranges for variables without normal distribution. For categorical variables (sex, educational level, severity), both absolute and relative frequencies will be presented.

For the inferential analyses, Spearman’s correlations will be used to explore relationships among questionnaires (stress, burden, and quality of life) as well as to correlate caregiver outcomes (stress, burden, quality of life) across subgroups defined by sociodemographic variables (e.g., economic status, education level), child-related variables (e.g., severity of Cerebral Palsy, mobility), and caregiving factors (e.g., relation with the child). Primary analyses will use multivariable linear regression to model each caregiver outcome: (i) perceived stress (PSS-14), (ii) caregiver burden (ZBI), and (iii) quality of life (PedsQL-FIM total). Separate regression models are specified for stress, caregiver burden, and quality of life, consistent with their conceptualization as co-primary constructs, each examined to characterize different but interrelated dimensions of caregiver outcomes. Given the finite population constraints (approximately 40 eligible caregivers)), each model will include only the most relevant predictors (up to 2–3 per model), carefully selected on priori literature and clinical plausibility (e.g., socioeconomic status, caregiving duration, and child functional severity/mobility). This parsimonious approach reduces multiple comparisons and allows adjustment for potential confounders. Model assumptions, including linearity, normality of residuals, and homoscedasticity, will be evaluated using standard diagnostics such as residual plots and Shapiro-Wilk tests. If model assumptions are violated, data transformations or alternative statistical techniques will be considered. Results will be reported as standardized regression coefficients (β) with 95% confidence intervals. Analyses will be conducted using IBM SPSS Statistics v28 (or equivalent software) with significance level of α = 0.05 (two-tailed).

Qualitative data.

Interviews will be audio- or video-recorded, transcribed verbatim, and analysed using a thematic analysis approach. Both deductive coding (guided by the quantitative findings and existing literature) and inductive coding (to capture emerging themes) will be applied. Codes will be organized into categories and higher-level themes to reflect caregivers lived experiences, coping strategies, and unmet needs. Two researchers will independently code a subset of transcripts to ensure inter-coder reliability, and discrepancies will be resolved through discussion until consensus is reached. Triangulation across researchers will further enhance validity. ATLAS.ti software will be used to manage and code the data [27,28]. It is anticipated a qualitative sample of approximately 10–15 participants, although data collection will continue until saturation is reached, defined as the point where no new relevant themes emerge. The approach will follow the Consolidated Criteria for Reporting Qualitative Research. This approach allows for analysis of the data with a set of expected themes informed by previous knowledge or research [29]. Integration of qualitative findings with quantitative results will be achieved through joint displays, side-by-side comparisons, and narrative weaving, allowing a comprehensive interpretation of caregiver outcomes and experiences. The first author will handle the interview analysis, while a different researcher will be involved in information triangulation to ensure the validity and reliability of the materials [30]. Subsequently, all authors will contribute to interpreting the data.

Dissemination plans.

The results of the study will be communicated to participants, healthcare professionals, and the broader public through several channels. Findings will be reported in the corresponding clinical trial registry, submitted for publication in peer-reviewed journals, and presented at relevant scientific conferences. A plain language summary will be prepared and made available to participants upon request. Additionally, healthcare providers involved in the study will receive a summary of the main outcomes to support the translation of findings into practice. Upon completion of the study, all anonymized quantitative datasets (including summary scores and data points underlying statistical analyses) and de-identified coded qualitative transcripts will be deposited in Zenodo (DOI 10.5281/zenodo.18435559) and made publicly available without restriction. Quantitative data will be shared in CSV format, and qualitative data in PDF/TXT format. To ensure participant confidentiality, all personal identifiers will be removed prior to data sharing. Any additional supporting information will be provided as supplementary files at the time of publication.