Background
Improved treatment programs and care over the past thirty years have substantially increased the proportion of children surviving cancer and today approximately 80% survive long term [
1]. However, surviving cancer during childhood imposes a number of physical and psychosocial difficulties later in life. These include school and work-related problems, difficulties related to friendships and intimate relationships, sleep disturbance, infertility and physical and emotional distress. These problems can have an immediate and negative impact on the quality of life (QoL) later in life [
2]. It has thus become important to measure long-term effects and quality of life of survivors of childhood cancer [
1].
The concept of QoL is mostly based on literature concerning adults [
3]. The World Health Organization defines QoL as “
the individuals’ perceptions of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns”
[
4]. QoL is a broad concept of general well-being, broader than health related quality of life (HRQoL) that is more specific and refers to the impact of health and illness [
2,
3,
5]. However, the perceptions of children and young people of their health and QoL differ from those of adults. Important factors in relation to QoL for young people are developmental stage and relationships with friends and family [
3]. It is also well known that children and parents rate the child’s health and QoL differently. Measuring children’s QoL by asking parents or another proxy respondent can only supplement but not replace responses from the child him/herself [
6‐
8]. Furthermore, the concept of QoL reflects the views of the individual (WHO, 1998) and thus the individual, in this case a child or a young person, should as far as possible rate his/her own QoL.
Various generic or disease-specific instruments exist for measuring QoL or HRQoL among children and adolescents [
9,
10] and in recent years there has been an increase in the number of instruments, particularly disease-specific instruments [
10]. Examples of generic instruments are the Child Health Questionnaire (CHQ-87), the PedsQL 4.0 and the KIDSCREEN-52 questionnaire [
9,
11]. Examples of instruments developed as disease-specific are the Pediatric Oncology Quality of Life scale (POQOL), PedsQL 3.0 cancer module and the Minneapolis-Manchester Quality of Life instruments (MMQL) [
9], however these instruments have also proved to capture generic aspects of QoL and HRQoL [
9]. Generic instruments allow comparison between groups, such as cancer survivors and the general population, and across different conditions or settings. If the objective is to measure the impact of illness on a person’s life, generic instruments lack the sensitivity and may not adequately cover specific concerns for, for example, cancer [
2,
10].
When assessing the HRQoL of children, their perception of health and QoL, their developmental changes and their cognitive function, are factors that should be considered [
3,
6]. Savage et al. [
6] found three disease-specific measures (MMQL-Youth Form, PedsQL™4.0, Pediatric Cancer Quality of Life-32) with sound psychometric properties in their review of QoL in children with acute lymphoblastic leukemia and only MMQL-Youth Form and PedsQL included age appropriate versions [
6]. The MMQL instrument has, in comparison with other health status and QoL instruments developed for children, proved to better capture the QoL perspective of health [
9]. Furthermore, the items used have a mainly positive phrasing, which is important for how each item is perceived and for the child’s experience of contributing to the questionnaire [
9].
The MMQL instrument was developed in three versions to meet developmental needs of different age groups and is based on extensive exploratory work with children [
12,
13]. The MMQL-Youth Form was created for evaluation of children (8–12 years of age) [
13] and the MMQL-Adolescent Form for evaluation of adolescents (13–20 years of age) [
12] surviving from cancer. There is also a version for adult individuals between 21–45 years of age [
12,
14]. The questionnaire consists of 4 subscales in the Youth Form [
13], and of 7 subscales in the Adolescent Form [
12]. Internal consistency reliability has been reported for the MMQL-Youth Form (overall alpha = 0.85, range 0.72 - 0.80) [
13], and for the MMQL-Adolescent Form (overall alpha = 0.92, range 0.67 - 0.89) [
12]. The test-retest reliability has been reported for MMQL-Youth Form as ranging from 0.56 to 0.79 and for the total scale as 0.72 [
13], and for the MMQL-Adolescent Form ranging from 0.60 to 0.90 and for the total scale as 0.71 [
12].
The MMQL-instrument has been used in surveys in the United States [
14,
15], the UK [
16] and in Denmark [
17]. In the UK they performed an adaptation of the MMQL instrument with healthy children, children with chronic conditions and children with cancer between 8–18 years of age [
16] and the Danish version of the MMQL-instrument was used in a survey with survivors of childhood brain tumors [
17]. Wu et al. [
15] compared adolescents with cancer, off-therapy survivors and patients on therapy, with healthy controls. They selected the MMQL instrument because they found the items generic enough to be administered in its entirety on healthy controls [
15]. Thus, as the MMQL instrument has been applied to numerous conditions involving both healthy children and children affected by or with experience from disease [
6,
15,
16] it can be used for evaluation of generic aspects of health. According to Streiner and Norman [
18] a questionnaire must be re-evaluated when it is used on a different sample or when it is translated into another language. The aim of this study was thus to evaluate the psychometric properties of the Swedish version of MMQL-Youth Form and the Adolescent Form on school children focusing on: 1) face and content validity 2) the internal consistency and 3) the test-retest reliability.
Results
The results concerning the face and content validity showed that the respondents understood the statements in the questionnaire and assessed that they had sufficient clarity and readability. Furthermore they evaluated the items as being relevant for the focus of the measure, for example one respondent wrote “It’s good that the questions are about how one feels about one’s health”.
The Cronbach
’ s alpha coefficient for the total scale was 0.88 for the MMQL-Youth Form (subscales from 0.66 to 0.81) and 0.92 for the MMQL-Adolescent Form (subscales from 0.69 to .91) (Table
2).
Table 2
Cronbach’s alpha coefficient for the MMQL-Youth form and adolescent form
Physical functioning | .66 | |
Psychological functioning | .81 | |
Physical Symptoms | .68 | |
Outlook on life/family dynamics | .78 | |
Physical functioning | | .69 |
Cognitive functioning | | .86 |
Psychological functioning | | .83 |
Body image | | .78 |
Social functioning | | .85 |
Outlook on life | | .91 |
Intimate relations | | .75 |
MMQL overall scale
| .88 | .92 |
The test-retest reliability according to ICC ranged from 0.43 - 0.78 for the original instrument MMQL – Youth Form (Table
3). Sixteen of the items (50%) showed good agreement and the remaining 16 items showed moderate agreement between the two occasions.
Table 3
Intraclass correlation coefficients (ICC) for the original instrument MMQL – Youth Form (n = 110)
1. I do as well as my friends in sports | 108 | 0.527 | 0.38 - 0.65 |
2. I have a lot of energy | 107 | 0.654 | 0.53 - 0.75 |
3. I have a lot of energy for running or sports | 105 | 0.759 | 0.67 - 0.83 |
4. I cannot do many activities because of my health | 107 | 0.552 | 0.41 - 0.67 |
5. I cannot do many activities because of problems with my arms or legs | 107 | 0.490 | 0.33 - 0.62 |
6. In games and sports, I like to watch rather than take part | 107 | 0.567 | 0.42 - 0.68 |
7. Sad? | 108 | 0.527 | 0.38 - 0.65 |
8. Angry? | 108 | 0.637 | 0.51 - 0.74 |
9. Lonely? | 108 | 0.464 | 0.30 - 0.60 |
10. Frightened? | 107 | 0.648 | 0.52 - 0.75 |
11. Worried about dying? | 107 | 0.710 | 0.60 - 0.79 |
12. Worried about your health? | 108 | 0.471 | 0.31 - 0.61 |
13. Worried about things in general? | 104 | 0.524 | 0.37 - 0.65 |
14. Not as good as most people? | 107 | 0.432 | 0.27 - 0.57 |
15. My parents treat me in the same way they treat my brothers and sisters | 105 | 0.571 | 0.43 - 0.69 |
16. My parents are usually patient with me | 103 | 0.759 | 0.66 - 0.83 |
17. feel different from your friends | 106 | 0.508 | 0.35 - 0.64 |
18. Do you have pain or discomfort in your stomach or tummy? | 106 | 0.515 | 0.36 - 0.64 |
19.Do you have headahes? | 107 | 0.637 | 0.51 - 0.74 |
20. Do your arms and legs ache? | 108 | 0.634 | 0.51 - 0.73 |
21. Do you have discomfort in yor chest during active exercise? | 106 | 0.600 | 0.46 - 0.71 |
22. Do you get pains that wake you up at night? | 107 | 0.660 | 0.54 - 0.76 |
23. Do you have difficulty with your hearing? | 108 | 0.713 | 0.61 - 0.78 |
24. Do you have difficulty with your talking (e.g., stuttering/stammer)? | 107 | 0.731 | 0.63 - 0.81 |
25. Do you have difficulty seeing clearly (even wearing glasses)? | 107 | 0.481 | 0.32 - 0.61 |
26. Do you have difficulty falling asleep? | 108 | 0.686 | 0.57 - 0.78 |
27. I am looking forward to the future | 108 | 0.630 | 0.50 - 0.73 |
28. I am happy the way things are | 109 | 0.557 | 0.41 - 0.67 |
29. I am happy with the state of my health | 108 | 0.648 | 0.52 - 0.75 |
30. I am happy with my life in general | 109 | 0.781 | 0.70 - 0.85 |
31. I am a healthy person | 109 | 0.775 | 0.69 - 0.84 |
32. I expect to live a long life. I expect to grow old | 108 | 0.584 | 0.44 - 0.70 |
The ICC for the MMQL – Adolescent Form ranged from 0.24 - 0.76 (Table
4). Ten of the items (22%) showed good agreement, 26 items (58%) showed moderate agreement and 9 items (20%) showed fair agreement between the two occasions.
Table 4
Intraclass correlation coefficients (ICC) for the original instrument MMQL – adolescent form (n = 120)
1. I have a lot of energy | 119 | 0.477 | 0.33 - 0.61 |
2. I need time out to rest during the day | 118 | 0.532 | 0.39 - 0.65 |
3. I have a lot of energy for running or sports | 118 | 0.611 | 0.49 - 0.71 |
4. I cannot do many activities because of my arms or legs | 118 | 0.346 | 0.18 - 0.50 |
5. I cannot do many activities because of my health | 119 | 0.505 | 0.36 - 0.63 |
6. In games and sports, I like to watch rather than take part | 119 | 0.529 | 0.39 - 0.65 |
7. Sad | 119 | 0.698 | 0.59 - 0.78 |
8. Angry | 119 | 0.587 | 0.46 - 0.69 |
9. Tired during the day | 119 | 0.571 | 0.44 - 0.68 |
10. Lonely | 118 | 0.686 | 0.58 - 0.77 |
11. Frightened | 119 | 0.429 | 0.27 - 0.57 |
12. Anxious or nervous | 117 | 0.433 | 0.27 - 0.57 |
13. Strong and healthy | 117 | 0.370 | 0.20 - 0.52 |
14. Worried about dying | 119 | 0.637 | 0.52 - 0.73 |
15. Worried about my health | 118 | 0.396 | 0.23 - 0.54 |
16. Worried about things in general | 115 | 0.331 | 0.16 - 0.48 |
17. Not as good as most people (inferior to them) | 119 | 0.361 | 0.20 - 0.51 |
18. How satisfied are you with your weight? | 118 | 0.447 | 0.29 - 0.58 |
19. How happy are you with the way you look? | 115 | 0.571 | 0.43 - 0.68 |
20. How do you feel about your body development right now? | 114 | 0.248 | 0.68 - 0.41 |
21. I like my body the way it is | 118 | 0.590 | 0.46 - 0.70 |
22. When others look at me they think that I am poorly developed | 116 | 0.620 | 0.49 - 0.72 |
23. I am uncomfortable with the way my body is developing | 118 | 0.385 | 0.22 - 0.53 |
24. I find it difficult to make friends | 118 | 0.529 | 0.39 - 0.65 |
25. I feel left out in groups of people my own age | 117 | 0.549 | 0.41 - 0.67 |
26. People like to be with me | 116 | 0.538 | 0.39 - 0.66 |
27. I have a lot in common with my friends | 117 | 0.475 | 0.32 - 0.60 |
28. I get along well with people own age | 118 | 0.374 | 0.21 - 0.52 |
29. I have many close friends | 117 | 0.581 | 0.45 - 0.70 |
30. I have similar hobbies and interests to those of people my own age | 118 | 0.648 | 0.53 - 0.74 |
31. Being togheter with other people gives me a good feeling | 118 | 0.357 | 0.19 - 0.51 |
32. Do you have difficulty concentrating at school? | 118 | 0.544 | 0.40 - 0.66 |
33. Do you have difficulty concentrating at other times (e.g., playing cards, computer games or reading) | 118 | 0.566 | 0.43 - 0.68 |
34. How often is homework or study hard for you? | 116 | 0.638 | 0.52 - 0.73 |
35. How often do you need more help with school work than others in your class? | 118 | 0.437 | 0.28 - 0.57 |
36. How much difficulty do you have remembering things at school/college or work? | 117 | 0.550 | 0.41 - 0.66 |
37. How much difficulty do you have concentrating at work or school? | 117 | 0.624 | 0.50 - 0.72 |
38. How much difficulty do you have with reading and writing? | 117 | 0.582 | 0.45 - 0.69 |
39. How much difficulty do you have with math and calculation? | 116 | 0.562 | 0.42 - 0.68 |
40. How much difficulty do you have with your school work, compared to others in your class? | 116 | 0.591 | 0.46 - 0.70 |
41. I find it easy ti have an intimate relationship | 116 | 0.612 | 0.48 - 0.71 |
42. I am confident when I am with people of the opposite sex | 115 | 0.763 | 0.67 - 0.83 |
43. I am happy with the way things are | 117 | 0.519 | 0.37 - 0.64 |
44. I am happy with life in general | 116 | 0.589 | 0.46 - 0.70 |
45. In general, I am satisfied with my current life situation | 117 | 0.516 | 0.37 - 0.64 |
Discussion
This study assessed the psychometric properties of the Swedish version of the MMQL-Youth Form and Adolescent Form in a sample of Swedish children from 6
th and 9
th years in seven primary schools in a county in western Sweden. The results in the present study indicate that the Swedish versions of the MMQL-Youth Form and Adolescent Form are valid instrument for self-report measurement of Swedish children’s HRQoL. The questionnaires were validated in terms of face and content validity and participating children appraised that the items were relevant and that the questionnaires had sufficient clarity and readability. Children should be involved in instrument development and validation [
10] and an explanation for why respondents felt the questionnaires easy to understand and to fill out could be that 20 children were involved in the translation and interpretation procedure. A strength in the present study is that the sample was large and diverse with regard to socioeconomic background by including children from schools in different neighborhoods and that the response rate was high. A reason for the high response rate could be that researchers stayed in the classroom during the data collection and informed the children about the objectives of the study. Informants gave positive responses on participation like, “it feels good to be able to help in such things”.
The internal consistency of the MMQL-Youth Form in this sample was found to be acceptable for the total scale with an alpha coefficient of 0.88. This Cronbach’s alpha value is quite similar to the first test of Cronbach’s alpha by Bhatia et al. [
13]. An exception in the present study is the subscale Physical Functioning with an alpha coefficient of 0.66, not attaining the acceptable alpha of 0.70. In the first test by Bhatia et al. [
13] this subscale reached an alpha coefficient of 0.78. A reason for this discrepancy could be that the respondents in the present study were healthy children and that some of the items are more valid when having an illness. A low internal consistency value on physical functioning has also been found in other studies with children [
23] and future research will be important to investigate if internal consistency differs in samples of children affected by disease. The internal consistency of the MMQL-Youth Form in the present study is comparable with other instruments such as PedsQL™ and the European KIDSCREEN-52 for the measurement of HRQoL for children [
11,
24]. The stability of the scale over time with a two-week span that is deemed to be suitable for assessing the stability of a questionnaire [
18] showed that 50% of the items in the MMQL-Youth Form demonstrated good agreement and 50% moderate agreement between the test and retest. The ICC values for the MMQL-Youth Form in the first test by Bhatia et al. [
13] also showed moderate to good agreement between the test and retest (ICC ranged from 0.56- 0.79). The ICC values for the KIDSCREEN-52 ranged from 0.56-0.77 [
11] which is quite similar to the ICC values in the test of MMQL-Youth Form by Bhatia et al. [
13] and in the present study.
Both Bhatia et al. [
13] and Shankar et al. [
14] administered the questionnaire MMQL-Youth Form to the children (8 to 12 years old) in the form of face-to-face interviews. In the present study children were in the 6
th year of primary school and completed the MMQL-Youth Form by themselves. However, researchers and/or teachers were present in the classroom and when needed could explain the items for the children. Our procedure shows that it is feasible to let the children in this age group answering the questionnaire independently when they have the possibility to have the items explained. This is supported in a review by Riley [
25] who found that children in this age group can successfully self-report age-appropriate health related quality of life questionnaires. Whether also younger children (8 to 10 years old) can complete the MMQL-Youth Form independently and what support is needed for this could be the focus of future studies. Interview-administered questionnaires can be applied when the children are unable to read or write and can have some advantages. The number of items omitted can be reduced and the interviewer has the possibility of rephrasing the question or to probing for a more complete response [
18]. However, more time and cost efficient alternatives of administration, like the one described here, increase the usefulness of the instrument.
The internal consistency of the MMQL-Adolescent Form in this sample was found to be acceptable for the total scale as well as for the subscales. The alpha coefficient of 0.92 for the total scale is indicating a high level of reliability and is the same as for the first test by Bhatia et al. [
12]. The internal consistency of the Adolescent Form in the present study can be compared with other instruments for measurement of HRQoL for similar age group such as the CHQ-CF instrument with an alpha coefficient between 0.69-0.92 for the subscales [
26]. The stability of the scale over time with a two-week span showed that the ICC ranged between 0.248 and 0.763, with 80% of the items having moderate or good agreement and 20% fair agreement between the test and retest. In the test of the MMQL-Adolescent Form by Bhatia et al. [
12] the ICC score ranged between 0.60 – 0.90 for the subscales. ICC values for each item are, to our knowledge, not available [
12]. Having only a fair agreement level for some items may be due to a number of issues, for example, changing perceptions of informants between the first and second measurement. Conditions that may change over short intervals are, for example, anxiety, mood or pain [
18,
22]. This could thus indicate that the instrument is sensitive to changes and that a low ICC value does not necessarily mean that the instrument is unstable. This explanation is supported by the fact that feelings appear to change quickly among adolescents dependent on what happens in their everyday life [
27]. There is thus a need for further research of stability of the Swedish version of MMQL-Adolescent Form.
Some methodological considerations should be discussed. The ICC values were only fair for some subscales in the MMQL-Adolescent Form, it can be seen as a strength that the instrument captures mild changes over time. However, the results would have been strengthened if the children taking part in the retest were asked to respond to whether they felt better, worse or the same. Then the test-retest reliability could have been evaluated based on the children who reported no change in wellbeing. Future studies comparing children reporting change or no change in wellbeing within a short time frame would be important to evaluate the responsiveness of the instrument to mild changes. Evaluating the discriminate validity was beyond the scope of this study. In another study the instruments were able to distinguish between HRQoL in children with different age, gender and socio-economic conditions both for MMQL-Youth Form as well as for MMQL-Adolescent Form (unpublished observation, Hutton et al., submitted April 2013). Additional studies including children with different diagnosis i.e. cancer will be required to establish if the instrument is reliable and valid for subjects with different conditions especially if combined with a construct validity evaluation.
Competing interest
The authors declare that they have no competing interest.
Authors’ contribution
All of the authors have contributed in this study with design and instrument development, data collection and interpretation of the results as well as contributed in article writing to the final version. The study was originally designed by PS and JN. The manuscript was drafted by E-LE with supervision of PS and JN. Critical revisions for significant intellectual content were made by all authors. All authors read and approved the final manuscript.