Study population
This study was carried out in the context of a wider study to anglicise and shorten the Manchester-Minneapolis Quality of Life Survey for children (MMQL-UK (CF))[
20]. The MMQL-UK (CF) was used as the basis for the development of an adult form (MMQL-UK (PF)).
Before wider administration of the MMQL-UK (PF) could take place, the phrasing of the questions from the child form had to be modified to make them adult oriented. This was done by qualitative methods. An opportunistic sample of 15 parents of school children (age range 10–18) were recruited for interviews from a local school known to one of the researchers (PU) for development of the MMQL-UK (PF). During the interviews parents were asked to comment on the wording and structure of the questionnaire as well as completing a draft parent form. Interviews were carried out either at the home or at Swansea University, depending on the preference of the parent.
The newly developed MMQL-UK (PF) was then compared with the shortened and anglicised version of the MMQL-UK (CF). This paper concentrates specifically on the validation of the MMQL-UK (PF) and comparison with the child (CF) version. The Anglicisation and validation of the MMQL-UK (CF) is reported elsewhere [
20]. Although the original MMQL form was developed to measure HRQL in cancer survivors the anglicised MMQL-UK (CF) was developed for use with both healthy and chronic conditions. The MMQL-UK (PF) was therefore developed to be suitable for the same populations (i.e. healthy and chronic conditions).
Children and their parents or carers who met the inclusion criteria (see Table
1) were approached to take part in the study comparing the child and parent MMQL. Four chronic conditions (asthma, diabetes, chronic inflammatory bowel disease (IBD) and allogenic bone marrow transplant (BMT) following acute lymphoblastic leukaemia (ALL)) were chosen as exemplars for the study. In addition 'looked after' children in public care were recruited as a fifth exemplar. These groups were chosen to ensure a cross section of conditions varying in chronicity and degree of self-care involved and for their diverse impact on the different domains of childhood HRQL. Children with a chronic health problem were identified with the guidance of collaborating clinicians. Children in public care were identified through looked after assessments.
Table 1
Inclusion criteria for children and parents entering the study
Asthma | Children aged 8–18 years with moderate/severe asthma according to definitions given by the British Thoracic Society and their parents |
Diabetes | Children aged 8–18 with Type 1 Diabetes Mellitus and their parents |
IBD | Children aged 8–18 fulfilling diagnostic criteria for Crohn's Disease and Ulcerative Colitis and their parents |
BMT | Children aged 8–18 years at least six months post treatment for ALL and their parents |
Public care | Children aged 8–18 years in public care and their carers |
Controls | Healthy children aged 8–18 years from local schools |
Where possible, written information was sent out to the families of children with a chronic health condition one week before a routine outpatient appointment. On attendance at the clinic, a researcher provided a further verbal explanation of the study, took written consent and supervised completion of the questionnaires. Families of children not due in clinic during the data collection period were sent written information along with a reply form on which they could indicate their interest in the study. Telephone contact was made with families responding positively, to provide further verbal feedback about the study. Arrangements were made for families agreeing to take part to complete the questionnaire either in clinic or at home. Children in public care and their carers were provided with verbal and written information when attending paediatric assessments. If families expressed an interest in the study, arrangements were made for a home visit, where the interviewer gained informed consent and questionnaires were completed.
Participants for the control group were recruited from schools in Swansea, Neath, Port Talbot and Bridgend (Wales, UK). The control group were healthy children (and their parents) who were not currently using health care resources for any serious condition. Participants were given a screening questionnaire prior to participation that included a section about health status. Anyone who was identified as having a health problem was excluded from participation in the study. Permission to approach schools was obtained from the Directors of Education in each Local Education Authority, before selecting schools via multi-stage sampling. Information was sent to head teachers of sampled schools, inviting their school to participate. A researcher visited schools expressing an interest, to discuss the project further and arrange for data collection. Written information for parents, parental consent forms and parent questionnaires were supplied for each child to take home. Parents were asked to complete their questionnaires at home and return them to school by a specified date, along with consent for their child to complete the questionnaires. It was emphasised that completion of questionnaires should not involve consultation with the child. For those children that had parental consent, re-explanation and completion of questionnaires followed in class a week later, under the supervision of the researcher.
In both subject and control groups, children with moderate to severe learning difficulties and children and parents for whom English was not their first language were excluded from the study.
The study was approved by the Welsh Multi-centre Research Ethics Committee (MREC). Informed consent was sought from all children (subjects and controls) and their parents or those with parental responsibilities (for children less than 16 years of age), following oral and written explanation of the study.
Analysis
Data were analysed using the Statistical Package for Social Sciences (SPSS) version 11.4.
Assessing internal consistency
The internal consistency of the MMQL-UK (PF) components were assessed by item-total correlations and Cronbach's alpha [
23]. Questions yielding item-total correlations below 0.4 were considered for rejection [
24]. Questions were also considered for rejection if more than 75% of individuals gave the same response, because such questions are not sensitive enough to discriminate between different levels of severity [
24]. Questions were also considered for exclusion if they were disliked or considered difficult to answer by the parents completing them. Cronbach's alpha for each of the resulting components should exceed 0.7 [
25]. Principal components analysis was then performed on the parent content without any restrictions on the data and the structure was compared to the emergent structure from the child form. This was carried out in order to validate the underlying components of the MMQL-UK (PF).
Assessing validity
The construct validity of the MMQL-UK (PF) components were assessed by comparing them with the appropriate parent PedsQL™ quality of life scales. If the components were valid measures of HRQL, they would be expected to show significant small to moderate levels of correlation with each of the PedsQL™ scales, with the largest correlations being seen between the PedsQL™ scales measuring physical, social, emotional and school function and the comparable MMQL-UK (PF) components.
The discriminant validity of the MMQL-UK (PF) was assessed by comparison of component scores between parents whose children were being treated and the parents of the control group. Our a priori hypothesis was based on identifying moderate to large differences in effect size between each exemplar and the control group [
26]. If the components were valid measures of HRQL, the exemplar groups would be expected to score lower on the MMQL-UK (PF) components than the control group. Independent samples t-tests with Bonferroni corrections were used to compare control and exemplar groups. Differences in component score between the exemplars and control groups were also reported as effect sizes where 0.2–0.49 represented a small difference, 0.5–0.79 represented a moderate difference and greater than 0.8 represented a large difference [
26].
The relationship between the MMQL-UK (CF) and MMQL-UK (PF) was determined using Pearson's correlation. If the two reports measure the same concept, then moderate correlation would be expected between the component scores of the MMQL-UK (CF) and the MMQL-UK (PF).
Assessing reproducibility
Following initial completion of the MMQL-UK (PF) by parents of the exemplar group children, they were asked to complete a second 'retest' questionnaire the next time their child visited clinic. This was a maximum of three months after the first assessment. In addition to completing the MMQL-UK (PF), the parents of children were asked to rate whether they thought their child's health had changed (improved, got worse or stayed the same) since the first questionnaire was completed. Those parents reporting no change were included in the reproducibility analysis. Reproducibility was assessed using intra-class correlation co-efficient [
27].
Assessing responsiveness
The responsiveness of the MMQL-UK (PF) was assessed by using the scores of the exemplar group parents who reported a change in their child's health. The response ratio (mean change in scores for subjects reporting a change divided by the standard deviation of the subjects reporting no change) was used to quantify the responsiveness [
27]. The larger the ratio, the more responsive the instrument.