Study design and participants
An observational, analytical cohort study was conducted with the Y-5L, Y-3L, PedsQL and SRH question. A head-to-head comparison of the Y-5L and Y-3L instrument performance is presented elsewhere [18, 21].
Three research settings, each with children/adolescents in different health states, were used in Cape Town, South Africa. Although details of socio-economic status were not captured children living in the same geographical area were recruited ensuring that they were from similar socio-economic backgrounds (low to middle income).
Children/adolescents attending two mainstream schools, which admit generally healthy learners without special education needs, were used to recruit a general population sample. Children/adolescents with stable chronic health conditions were recruited from five schools for learners with special education needs. These schools have specialised education services for learners with normal intellect diagnosed with physical disability and/or learning disability. Children/adolescents requiring acute medical treatment were recruited from the inpatient wards of an acute tertiary paediatric hospital and a paediatric orthopaedic hospital.
All children/adolescents aged 8–15 years, who were able to read and write English, the most commonly spoken and written language in South Africa , at each facility were eligible for the study. Only those who returned a signed informed consent and assent were included in the study and those who were critically ill or who were medically unstable were excluded as the research may have been too distressing. The sample size was adequately powered (95%) to detect a difference in correlation of scores between the three condition groups with a small effect size 0.4 and a significance of 0.05.
The official Y-3L English version for South Africa was used in this study. The experimental Y-5L English version for the United Kingdom was tested for equivalence in English for South Africa by the EuroQol group . Each version consists of five dimensions namely Mobility (walking about), Looking After Myself (washing and dressing), Usual Activities (going to school, hobbies, sports, playing, doing things with family or friends), Pain or Discomfort and Worried, Sad, or Unhappy. There is also a general rating of health on a VAS of 0 (worst health) to 100 (best health). The original youth version, Y-3L, describes health on three levels (no problems, some problems and a lot of problems) resulting in 243 (35) health states [16, 24]. The newly expanded version, Y-5L, describes health on five levels [no/not, a little bit, some/quiet, a lot/really, cannot/extreme(ly)] resulting in 3125 (55) health states.
The three or five levels of the descriptive system are expressed with a five-digit code. For example, the Y-3L health state 11223 describes someone with no problems with Mobility, no problems with Looking After Myself, some problems with Usual Activities, some Pain or Discomfort and very Worried, Sad or Unhappy. The best health state described by the instrument is coded as 11111, describing ‘no problems’ in each of the dimensions . Although the Y-3L has a preference-based score the Y-5L does not [25,26,27]. As such a level sum score (LSS) was used to describe the responses on the descriptive system where the level labels are treated as numeric data with the best possible score (1 + 1 + 1 + 1 + 1) = 5 and the most severe score for the EQ-5D-Y-3L is (3 + 3 + 3 + 3 + 3) = 15. The other health states will have a LSS ranging between 5 and 15, with a larger score indicating a worse health state. Y-5L is similarly scored with a LSS ranging between 5 and 25 . The LSS is a crude score which does not account for preference of dimensions or weighting of responses [29, 30] but gives some indication of the performance of the dimensions between the Y-3L and Y-5L. Results from Y-3L value sets show that there is a difference in rank order of dimensions and scores attributed to dimensions when compared to the adult EQ-5D-3L [25,26,27] as such comparing LSS may give a better indication of performance of the Y-3L compared to the Y-5L than using the adult EQ-5D-3L and EQ-5D-5L value sets. The Y-5L VAS was reported for this study.
Pediatric Quality of Life Inventory (PedsQL)
The 23 item PedsQL 4.0 Generic Core Scales for children aged 8–12 years and 13–18 years were used as appropriate . Both age versions of the PedsQL consist of four dimensions of functioning: physical, emotional, social, and school with 8,5,5 and 5 items respectively. Each item is scored on a Likert scale from 0 to 4 (never a problem, almost never, sometimes, often, or almost always a problem). Items are reversed scored and transformed to a 0–100 scale: 0 = 100, 1 = 75, 2 = 50, 3 = 25, 4 = 0. Dimension scores are calculated by a sum of the item scores divided by the total number of items. A total score is similarly generated by summing the dimension scores over the total number of dimensions giving an overall Health Related Quality of Life (HRQoL) score. Scores for scales with more than 50% missing data are not computed. A higher PedsQL score indicates a better HRQoL [32,33,34].
Self-Rated Health (SRH)
The Self-Rated Health (SRH) question asks the child to describe their general health today as: ‘excellent’, ‘very good’, ‘good’, ‘fair’ or ‘poor’. This question has been shown to be a valid measure of subjective health in children and adolescents . The items were scored numerically for data analysis with excellent scored 5 and poor scored 1. The SRH question is expected to capture general health similarly to the EQ-5D-Y VAS [36, 37].
Ethics approval was obtained from the University of Cape Town, Faculty of Health Sciences, Human Research Ethics Committee (HREC 154_2019). The study was carried out in accordance with the declaration of Helsinki involving human participants  and the recommended Covid precautions.
Children/adolescents aged 8–15 years admitted to either of the acute inpatient hospital settings were recruited during an onsite visit. For those who were willing and provided consent and assent the parent was asked to complete the socio-demographic information for the child and the children/adolescents were asked to self-complete the Y-5L, PedsQL, SRH and Y-3L in that order. The Y-5L was presented first based on the adult study comparing the EQ-5D-5L and EQ-5D-3L version as it was found that if the EQ-5D-3L was presented first the additional levels on the EQ-5D-5L were not considered . Children and adolescents recruited at one of the hospitals completed the questionnaires in a quiet, private space with supervision from the researcher.
Due to the constraints of the Covid pandemic children and adolescents attending either the mainstream schools or schools for learners with special education needs were recruited through information leaflets that were sent home to them and their parents. For those who were willing and provided consent and assent the instruments were self-completed by the child/adolescent at home under the supervision of their parent. The accompanying information clearly stated that parents should not assist or influence with the completion of the instruments. A reminder was sent out to learners and parents who had not responded after one and two weeks.
Data management and analysis
General performance and feasibility
The Y-5L, Y-3L, PedsQL and SRH responses and descriptive data were summarised in terms of frequency of responses. The feasibility was assessed by comparing the number of missing values across measures.
The concurrent validity of the dimension scores of the Y-3L and Y-5L were compared to the individual PedsQL items and sub-scale scores using Spearman correlations (rs).
It was anticipated that Y-5L/Y-3L Mobility dimension would be associated with PedsQL items of hard to walk; 100 m, hard to run and Physical Health Summary Score. Y-5L/Y-3L Looking After Myself dimension would be associated with PedsQL hard to bath/shower. Y-5L/Y-3L Usual Activities would be associated with participate in sport/exercise, household chores, miss school because not feeling well, miss school to go to the doctor and Y-3L/Y-5L Worried, Sad or Unhappy would be associated with items of Sad and Worry. PedsQL summary and total scores were compared to EQ-5D-Y LSS and VAS and scores and SRH scores with the Pearson’s correlation co-efficient. Correlation coefficients were interpreted according to Cohen: 0.1–0.29 low association, 0.3–0.49 moderate association and ≥ 0.5 high association .
Children with health conditions receiving acute or chronic health care and those from the general population were compared for known-group validity. Analysis of variance (ANOVA) with Tukey post hoc analysis was used to compare the Y-5L and Y-3LL LSS and VAS scores, PedsQL sub-scales, summary and total scores and the SRH score (which was treated as a scale variable for this analysis).
All data analyses were conducted using SPSS Windows 27.0 (IBM SPSS Inc., Chicago, IL, USA) and Statistica Windows Version 13.0 (TIBCO Software Inc., Palo Alto, CA, USA).