Qual Life Res DOI 10.1007/s11136-014-0655-2
Psychometric properties of KIDSCREEN health-related quality of life questionnaire in Iranian adolescents Ahmad Shahabeddin Parizi • Gholamreza Garmaroudi Mojtaba Fazel • Sepideh Omidvari • Seyed Ali Azin • Ali Montazeri • Saba Jafarpour
•
Accepted: 19 February 2014 Ó Springer International Publishing Switzerland 2014
Abstract Introduction Health-related quality of life (HRQOL), which is receiving increasing attention, is a multidimensional concept that encompasses different areas including the physiological, psychological, social, and spiritual aspects of life. The KIDSCREEN-52 questionnaire is designed to measure the HRQOL of 8–18-year-old children and adolescents. The aim of this study was to develop a Persian version of KIDSCREEN-52 and analyze the validity and reliability of the translated version. Method The KIDSCREEN-52 was translated into Persian in keeping with the international cross-cultural translation guidelines. A cross-sectional study was performed in the city of Tehran during 2012–2013. 328 students ranging in age from 8 to 18 years were enrolled in the study. The reliability for each dimension was estimated using Cronbach’s alpha coefficient. To examine the validity of the A. S. Parizi School of Public Health, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] G. Garmaroudi (&) Department of Health Promotion and Education, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] M. Fazel Department of Pediatrics, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected]
questionnaire, a confirmatory factor analysis (CFA) was conducted. Results The Cronbach’s alpha coefficient was higher than 0.7 in all ten dimensions except self-perception. Validity of this questionnaire was confirmed by CFA. (Relative chi square (v2/df) = 1.73; root-mean-square error of approximation = 0.047; normed fit index = 0.93; Tucker–Lewis index = 0.97; comparative fit index = 0.97; and relative fit index = 0.92.) Conclusion The Persian version of KIDSCREEN-52 is reliable and valid and can be used as a self-administered instrument for measuring HRQOL in children and adolescents in Iran. Keywords Health-related quality of life KIDSCREEN Adolescents Validity
A. Montazeri e-mail: [email protected] S. A. Azin Reproductive Infections Research Group, Avecina Research Institute, ACECR, Tehran, Iran e-mail: [email protected] S. Jafarpour Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected]
S. Omidvari A. Montazeri Menal Health Research Department, Health Metrics Research Center, Iranian Institute for Health Sciences Research, ACECR, Tehran, Iran e-mail: [email protected]
123
Qual Life Res
Background
Table 1 Internal consistency of KIDSCREEN-52 in 13 European countries survey
Quality of life is a key concept in the health and medical professions. It is a subjective perception of well-being that varies between different individuals [1]. Health-related quality of life (HRQOL), which is receiving increasing attention, is a multidimensional concept that encompasses different areas including the physiological, psychological, social, and spiritual aspects of life [1–6]. This concept is closely related to WHO’s definition of health: ‘‘a state of complete physical, mental, and social wellbeing and not merely the absence of disease or infirmity’’ [7]. HRQOL used to be assessed mainly among adults, but in recent years increasing attention has been given to the assessment of HRQOL in children and adolescents [1, 8, 9]. Developing an appropriate instrument is vital for monitoring HRQOL. Tools designed for adults are not suitable for assessing HRQOL in children [1, 10]. Children’s emotions, cognitive development, and reading skills should be considered [1, 3, 9], and specific aspects of their lives including their relations with family, friends, and school must be taken into account [4]. By using the properly designed instrument, children and adolescent can reliably answer the HRQOL questionnaires and can therefore be assessed directly instead of according to the data provided by their mother or primary care giver [3, 11]. There are over a hundred instruments available for assessing HRQOL in children and adolescents [4]. Because the sense of wellbeing and being functional can be affected by cultural backgrounds, the measuring tool should be developed simultaneously among different cultures, or the existing accepted instrument should be translated, analyzed, and adapted into other languages considering the cultural diversities [12]. KIDSCREEN-52 is a psychometric sound health-related quality of life measure that was developed in the KIDSCREEN project conducted in 2001–2004 by Ravens-Sieberer et al. It is a self-report measure that assesses the HRQOL in both healthy and chronically ill children aged 8–18 years. It measures ten HRQOL dimensions: physical well-being, psychological well-being, moods and emotions, self-perception, autonomy, parent relations and home life, social support and peers, school environment, social acceptance (bullying), and financial resources. The project was conducted by the study center at Robert Koch Institute in Berlin, Germany together with twelve European countries, including Austria, Czech Republic, France, Greece, Hungary, Ireland, Poland, The Netherlands, Spain, Sweden, Switzerland, and United Kingdom. As a result of the simultaneous development in thirteen different countries, KIDSCREEN questionnaires are cross-national instruments [9]. Several other versions of KIDSCREEN are also available, including Norwegian [1], Korean [3], Argentinean [4], Serbian [12] and Turkish [15].
Dimension
No. items
Cronbach’s a
Physical well-being
5
0.80
123
Psychological well-being
6
0.89
Moods and emotions
7
0.85
Self-perception
5
0.79
Autonomy
5
0.84
Parent relation and home life
6
0.88
Financial resources Social support and peers
3 6
0.89 0.84
School environment
6
0.87
Social acceptance/bullying
3
0.77
The aim of this study was to develop a Persian version of KIDSCREEN-52 HRQOL and analyze the validity and reliability of the translated version.
Methods Sample and data collection As a rule of thumb, the number of samples to validate a questionnaire varies from 4 to 10 subjects per variable [16]. It is also recommended that choosing a minimum 300 subject for a study is acceptable [17]. KIDSCREEN-52 is a questionnaire with 52 items, so a sample size with 300 subjects was chosen. This cross-sectional study was performed in the city of Tehran during 2012–2013. The eligible population for the study was all male and female children aged 8–18 years attending schools in Tehran. Schools in Iran are single sex. School education is divided into the following cycles: preschool (1 year cycle, children aged 5); Primary (6 year cycle, children aged 6–11); Middle (2 year cycle, students aged 12–13); High school (4 year cycle, students aged 14–18). Students of the third grade of primary school through fourth grade of high school (a total of ten grades) were eligible to enter the study. Tehran’s municipality has divided the city into 22 regions by the geographic location on the map. In this study, these regions were stratified by district into 5 strata (North, Center, South, West, and East). In each stratum, the schools were divided into two groups: girls’ schools and boys’ schools. Then, from each of these groups, one primary, one middle, and one high school were selected randomly; that made a sum of 6 schools in each stratum and a total of 30 schools in the study. In each grade 3, students were randomly chosen to enter the study. As a result, considering the ten eligible
Qual Life Res
grades, the total number of students enrolled in the study was at least 300. Schools that did not agree to participate were replaced by another randomly selected school from the same group in the stratum. Before performing the study, an approval was obtained from the ethical review committee of Tehran University of Medical Sciences. In each school, the students and their parents were given some information about the study, reassured that the given information would remain confidential, and written consent was obtained from the parents. Only those students whose parents had consented to their joining the study were included. The self-report instrument KIDSCREEN-52 HRQOL was given to the participants while an instructor was present.
Instrument The KIDSCREEN-52 questionnaire includes 52 items which are distributed among ten dimensions including physical well-being (5 items), psychological well-being (6 items), moods and emotions (7 items), self-perception (5 items), autonomy (5 items), parent relations and home life (6 items), financial resources (3 items), social support and peers (6 items), school environment (6 items), and social acceptance/bullying (3 items). Questions should be answered based on attitudes, moods, feelings, and behaviors in the previous week, and the items follow a 5-point Likert-type scale [18] with three different type of responses: (1) excellent, very good, good, fair, poor; (2) extremely, very moderately, slightly, not at all; (3) always, very often, quite often, seldom, never. Items which were negatively formulated were re-coded according to the manual handbook of KIDSCREEN [19]. Finally, the score of each dimension was transformed linearly to a 0–100-point scale. The reliability of the KIDSCREEN-52 questionnaire was perused in 13 European countries at 2007 [18], and the results are presented in Table 1. The KIDSCREEN-52 was translated into Persian according to international cross-cultural translation guidelines [20] and using the forward–backward–forward technique [21]: two independent translators who had Persian as their mother language translated the English version into Persian; these translations were assessed and compared by a group of experts, and the best translation was chosen for each item. Because the age range of the intended population group of this questionnaire is wide (from 8 to 18), the simplest and most familiar words and phrases were chosen [22]. This mixed translation was reverted to English by another professional translator. This version was sent to the KIDSCREEN committee and, after further confirmation by this committee; the mixed Persian version was used in this study.
Table 2 Internal consistency of Persian KIDSCREEN-52 Dimension
Mean (SD)
No. items
Cronbach’s a
Physical well-being
66.997 (21.688)
5
0.784
Psychological well-being
66.349 (22.570)
6
0.861
Moods and emotions
64.678 (20.954)
7
0.807
Self-perception
68.338 (20.301)
5
0.601
Autonomy
55.366 (23.965)
5
0.784
Parent relation and home life
68.191 (24.797)
6
0.876
Financial resources
55.919 (29.792)
3
0.841
Social support and peers
54.611 (21.079)
6
0.718
School environment
62.779 (23.171)
6
0.805
Social acceptance/ bullying Total
83.206 (19.848)
3
0.706
64.643 (8.469)
52
0.937
Table 3 Fit indices based on sum of scores of 10 dimensions Indices
Value
Recommended cutoff value
v2/df
1.73
B2
RMSEA
0.047
B0.05
NFI
0.93
C0.90
TLI
0.97
C0.90
CFI
0.97
C0.90
RFI
0.92
C0.90
Statistical analysis We used SPSS for Windows (20.0) for statistical analysis and Lisrel (version 3) for the confirmatory factorial analysis. The reliability of each dimension was estimated using the Cronbach’s alpha coefficient. Alpha coefficients equal to or higher than 0.7 were considered acceptable [23]. To examine the validity of the questionnaire, a confirmatory factor analysis (CFA) was conducted, which provided fitness indices to see how well the model fit the data. There were various recommendations in the literature regarding number, type, and cutoff values for the goodness-of-fit needed to be reported [1]. In this study, we used the following indices: relative chi square (v2/df) and root-meansquare error of approximation (RMSEA) as absolute fit measures and normed fit index (NFI), Tucker–Lewis index (TLI), comparative fit index (CFI), and relative fit index (RFI) as incremental fit measures. The acceptable cutoff point for incremental measures is 0.90. RMSEA values B0.05 and v2/df values B2 are regarded as a close fit. In order to assess the construct validity, item-scale correlation
123
Qual Life Res Table 4 Item-scale correlation coefficient Physical activities and health
Feelings
General mood
About yourself
Free time
Family and home life
Money matters
Friends
School and learning
Bullying
PAHQ1
0.674**
0.431**
0.320**
0.298**
0.219**
0.303**
0.272**
0.077
0.260**
0.185**
PAHQ2
0.764**
0.581**
0.356**
0.323**
0.322**
0.464**
0.255**
0.202**
0.482**
0.101
PAHQ3 PAHQ4
0.755** 0.738**
0.460** 0.384**
0.260** 0.221**
0.260** 0.259**
0.345** 0.263**
0.392** 0.302**
0.283** 0.211**
0.146** 0.172**
0.307** 0.255**
0.144** 0.123*
PAHQ5
0.730**
0.587**
0.330**
0.297**
0.310**
0.370**
0.195**
0.239**
0.467**
0.159**
FQ1
0.564**
0.826**
0.435**
0.432**
0.439**
0.547**
0.360**
0.169**
0.480**
0.144**
FQ2
0.456**
0.731**
0.452**
0.351**
0.335**
0.454**
0.262**
0.236**
0.454**
0.151**
FQ3
0.474**
0.798**
0.452**
0.427**
0.402**
0.487**
0.357**
0.152**
0.519**
0.209**
FQ4
0.511**
0.720**
0.380**
0.433**
0.424**
0.405**
0.305**
0.139*
0.435**
0.048
FQ5
0.561**
0.780**
0.365**
0.364**
0.365**
0.452**
0.238**
0.172**
0.432**
0.145**
FQ6
0.509**
0.762**
0.338**
0.301**
0.444**
0.450**
0.277**
0.313**
0.476**
0.174**
GMQ1
0.134*
0.196**
0.546**
0.210**
0.044
0.104
0.005
0.158**
0.110*
GMQ2
0.309**
0.396**
0.750**
0.394**
0.238**
0.326**
0.216**
0.102
0.253**
0.098
GMQ3
0.242**
0.290**
0.685**
0.259**
0.178**
0.271**
0.079
0.040
0.222**
0.066
GMQ4
0.316**
0.433**
0.735**
0.435**
0.237**
0.427**
0.249**
0.065
0.318**
0.187**
GMQ5
0.236**
0.328**
0.626**
0.273**
0.145**
0.277**
0.132*
-0.013
0.228**
0.065
GMQ6
0.331**
0.434**
0.725**
0.460**
0.209**
0.393**
0.236**
-0.047
0.285**
0.140*
GMQ7 AYQ1
0.335** 0.384**
0.408** 0.472**
0.694** 0.347**
0.434** 0.492**
0.304** 0.365**
0.356** 0.415**
0.296** 0.311**
0.076 0.120*
0.238** 0.362**
0.271** 0.122*
AYQ2
0.366**
0.556**
0.341**
0.598**
0.403**
0.556**
0.439**
0.179**
0.492**
0.205**
AYQ3
0.134*
0.191**
0.375**
0.660**
0.090
0.205**
0.231**
-0.009
0.110*
0.106
AYQ4
0.131*
0.128*
0.251**
0.644**
0.017
0.187**
0.109*
-0.073
0.163**
0.189**
AYQ5
0.213**
0.224**
0.313**
0.700**
0.177**
0.315**
0.084
0.023
0.230**
0.134*
FTQ1
0.282**
0.423**
0.185**
0.293**
0.747**
0.443**
0.395**
0.286**
0.292**
0.055
FTQ2
0.331**
0.436**
0.260**
0.295**
0.759**
0.446**
0.446**
0.303**
0.355**
0.068
FTQ3
0.303**
0.365**
0.171**
0.212**
0.796**
0.331**
0.426**
0.360**
0.230**
0.100
FTQ4
0.189**
0.254**
0.168**
0.129*
0.643**
0.262**
0.249**
0.422**
0.108
0.078
FTQ5
0.355**
0.427**
0.270**
0.300**
0.717**
0.442**
0.356**
0.282**
0.407**
0.071
FHLQ1
0.385**
0.451**
0.404**
0.430**
0.402**
0.802**
0.422**
0.225**
0.423**
0.232**
FHLQ2
0.366**
0.423**
0.290**
0.413**
0.310**
0.740**
0.383**
0.196**
0.525**
0.102
FHLQ3
0.464**
0.593**
0.385**
0.466**
0.513**
0.805**
0.438**
0.246**
0.472**
0.224**
FHLQ4
0.381**
0.534**
0.409**
0.461**
0.513**
0.820**
0.409**
0.316**
0.519**
0.235**
FHLQ5
0.414**
0.434**
0.361**
0.469**
0.366**
0.774**
0.378**
0.231**
0.462**
0.179**
FHLQ6 MMQ1
0.354** 0.291**
0.433** 0.336**
0.312** 0.188**
0.314** 0.330**
0.381** 0.487**
0.778** 0.437**
0.282** 0.892**
0.249** 0.265**
0.428** 0.313**
0.113* 0.201**
MMQ2
0.318**
0.378**
0.296**
0.384**
0.452**
0.486**
0.885**
0.289**
0.384**
0.154**
MMQ3
0.257**
0.304**
0.163**
0.253**
0.397**
0.349**
0.835**
0.326**
0.269**
0.136*
FrQ1
0.184**
0.268**
0.134*
0.089
0.435**
0.294**
0.300**
0.649**
0.241**
0.099
FrQ2
0.076
-0.110*
-0.164**
0.150**
0.153**
0.548**
0.007
0.118*
FrQ3
0.174**
0.193**
0.033
0.084
0.378**
0.303**
0.308**
0.715**
0.249**
0.124*
FrQ4
0.283**
0.290**
0.086
0.186**
0.315**
0.318**
0.196**
0.637**
0.388**
0.076
FrQ5
0.090
0.124*
-0.008
0.076
0.201**
0.156**
0.161**
0.626**
0.199**
0.002
FrQ6
0.089
0.153**
0.056
0.043
0.289**
0.178**
0.200**
0.705**
0.210**
0.016
SLQ1
0.368**
0.483**
0.268**
0.336**
0.283**
0.448**
0.216**
0.229**
0.767**
0.028
SLQ2
0.419**
0.481**
0.255**
0.359**
0.238**
0.447**
0.330**
0.170**
0.675**
0.146**
SLQ3
0.352**
0.477**
0.265**
0.346**
0.326**
0.426**
0.235**
0.227**
0.751**
0.048
SLQ4
0.386**
0.371**
0.247**
0.200**
0.283**
0.437**
0.323**
0.289**
0.565**
0.150**
123
-0.012
-0.018
-0.062
Qual Life Res Table 4 continued Physical activities and health
Feelings
General mood
About yourself
Free time
Family and home life
Money matters
Friends
School and learning
Bullying
-0.001
SLQ5
0.250**
0.327**
0.264**
0.268**
0.185**
0.354**
0.116*
0.179**
0.742**
SLQ6
0.306**
0.462**
0.241**
0.338**
0.316**
0.451**
0.376**
0.312**
0.756**
0.046
BQ1
0.108
0.090
0.145**
0.152**
0.083
0.041
0.029
0.038
0.747**
BQ2
0.170**
0.171**
0.159**
0.201**
0.115*
0.216**
0.175**
0.088
0.045
0.836**
BQ3
0.182**
0.188**
0.172**
0.220**
0.140*
0.244**
0.227**
0.146**
0.141*
0.797**
-0.020
* Correlation is significant at the 0.05 level (2-tailed). ** Correlation is significant at the 0.01 level (2-tailed)
coefficients were calculated. Construct validity was assumed if items showed the highest correlation with their original dimension.
Results 328 students were enrolled in the study. Of a total of 328 participants, 49.4 % were male and 50.6 % were female. Mean age of the participants was 12.9 ± 2.9, ranging from 8 to 18 years. Average scores of the 10 KIDSCREEN-52 dimensions along with Cronbach’s alpha coefficients are presented in Table 2. The means and SDs are shown in transformed metric scale ranging from 0 to 100. The Cronbach’s alpha coefficient is higher than 0.7 in all ten dimensions except self-perception, which is 0.601 (Table 2). Table 3 presents the CFA based on the sum scores of ten dimensions. The chi-square test of the model was statistically significant (df = 1,179, p value \0.001). Each items in the Persian KIDSCREEN correlated significantly higher to the dimension to which it was categorized than to the other nine dimensions. This can be interpreted as a good construct validity of the questionnaire (Table 4).
dimension could be acceptable. In a similar study, the alpha coefficient of less than 0.7 in two different dimensions was considered good enough for a measure that was developed for a different population [4]. Recently, CFA is increasingly used to examine the validity of the quality of life questionnaires, which provides fitness indices to see how well the model fit the data [6]. In our study, construct validity was assessed by CFA. The chi-square test was significant. Relative chi square was less than the recommended cutoff value. CFI, TLI, NFI, and RFI were above 0.90 and RMSEA was less than 0.05, confirming the construct validity of all dimensions. The main strengths of this study were the adequate sample size and random selection of subjects from different districts with diverse ethnical groups and socioeconomic levels that can be a good representative of the entire country. The limitation of our study was that the cross-sectional design did not provide information about probable changes in HRQOL in children over time. Further prospective studies should be carried out to investigate these changes. In conclusion, the Persian version of KIDSCREEN-52 is a reliable and valid measure adopted into the Persian language, which considers the cultural context and ethnical diversities. The questionnaire can be used as a self-administered instrument for measuring HRQOL in children and adolescents in Iran.
Discussion KIDSCREEN-52 is a self-report questionnaire that assesses the HRQOL in children aged 8–18 years and was developed in the KIDSCREEN project conducted by RavensSieberer et al. The aim of this study was to develop a Persian version of KIDSCREEN-52 considering the Iranian cultural background and to examine the validity and reliability of the adopted questionnaire. Internal consistency reliability of the KIDSCREEN questionnaire had an above-satisfactory cutoff value of 0.7 in all dimensions except for ‘‘About yourself’’. Considering the fact that the KIDSCREEN-52 was developed in European countries with different languages and cultural bases and that selfperception is not clearly discussed in Iranian culture in families or during pre-school education, the reliability of this
References 1. Haraldstad, K., Christophersen, K. A., Eidea, H., Nativgc, G. K., Helsetha, S., & The KIDSCREEN group Europe. (2011). Health related quality of life in children and adolescents: Reliability and validity of the Norwegian version of KIDSCREEN-52 questionnaire, a cross sectional study. International Journal of Nursing Studies, 48(5), 573–581. 2. Robitail, S., Sime´oni, M. C., Ravens-Sieberer, U., et al. (2007). Children proxies’ quality-of-life agreement depended on the country using the European KIDSCREEN-52 questionnaire. Journal of Clinical Epidemiology, 60(5), 469–478. 3. Hong, S. D., Yang, J. W., Jang, W. S., Byun, H., Lee, M. S., Kim, H. S., et al. (2007). The KIDSCREEN-52 Quality of life measure for children and adolescents (KIDSCREEN-52-HRQOL): Reliability and validity of the Korean version. Journal of Korean Medical Science, 22(3), 446–452.
123
Qual Life Res 4. Berra, S., Tebe´c, C., Esandie, M. E., & Carignanog, C. (2013). Reliability and validity of the KIDSCREEN-52 questionnaire to measure health related quality of life in the 8 to 18 year-old Argentinean population. Archivos Argentinos de Pediatrı´a, 111(1), 29–35. 5. Bullinger, M., Schmidt, S., & Petersen, C. (2002). DISABKIDS Group. Assessing quality of life of children with chronic health conditions and disabilities a European approach. International Journal of Rehabilitation Research, 25(3), 197–206. 6. Fayersm, P. M., & Machin, D. (2007). Quality of life. The assessment, analysis and interpretation of patient-reported outcomes (2nd ed.). London: Wiley. 7. Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference, New York, 19–22 June, 1946; signed on 22 July 1946 by the representatives of 61 States (Official Records of the World Health Organization, No. 2, p. 100) and entered into force on 7 April 1948. http://www. who.int/about/definition/en/print.html. 8. Tzavara, C., Tzonou, A., Zervas, I., & Tountas, Y. (2012). Reliability and validity of the KIDSCREEN-52 health related quality of life questionnaire in a Greek adolescent population. Annals of General Psychiatry, 11, 3. 9. Ravens-Sieberer, U., Gosch, A., Rajmil, L., et al. (2005). KIDSCREEN-52 quality-of-life measure for children and adolescents. Expert Review of Pharmacoeconomics and Outcomes Research, 5, 353–364. 10. Huebner, E. S., Valois, R. F., Suldo, S. M., Smith, L., McKnight, C., Seligson, J. L., et al. (2004). Perceived quality of life: A neglected component of adolescent health assessment and intervention. Journal of Adolescent Health, 34(4), 270–278. 11. Riley, A. W. (2004). Evidence that school-age children can selfreport on their health. Ambulatory Pediatrics, 4, 371–376. 12. Stevanovic, D., Tadic, I., Novakovic, T., Kisic-Tepavcevic, D., & Ravens-Sieberer, U. (2012). Evaluation the Serbian version of the KIDSCREEN quality-of-life questionnaires: Reliability, validity, and agreement between children’s and parents’ ratings. Quality of Life Research, 22, 1729–1737 13. Mazur, J. (2004). Development and initial psychometric analysis of the generic quality of life questionnaire for Polish children and
123
14.
15.
16.
17.
18.
19.
20.
21.
22. 23.
adolescents (KIDSCREEN-52). Medycyna Wieku Rozwojowego, 8(3 Pt 1), 513–533. Tebe, C., Berra, S., Herdman, M., et al. (2008). Reliability and validity of the Spanish version of the KIDSCREEN-52 for child and adolescent population. Medicina Clı´nica (Barc), 130(17), 650–654. Meral, B. F., & Fidan, A. (2013). The examination of psychometric properties of KIDSCREEN-short version on children with autism in Turkey. International Journal on New Trends in Education and their Implications, 4(2), 151–159. Vet, H. C. W., Ader, H. J., Terwee, C. B., & Pouwer, F. (2005). Are factor analytical techniques used appropriately in the validation of health status questionnaires? A systematic review on the quality of factor analysis of the SF-36. Quality of Life Research, 14, 1203–1218. Rouquette, A., & Falissard, B. (2011). Sample size requirements for the internal validation of psychiatric scales. International Journal of Methods in Psychiatric Research, 20, 235–249. Ravens-Sieberer, U., Gosch, A., Rajmil, L., Erhart, M., Bruil, J., Power, M., et al. (2008). The KIDSCREEN-52 quality of life measure for children and adolescents: Psychometric results from a Cross-Cultural Survey in 13 European countries. Value in Health, 11, 645–658. The KIDSCREEN Group Europe. (2006). The KIDSCREEN questionnaires quality of life questionnaires for children and adolescents Handbook. Lengerich: Pabst Science Publishers. WHOQOL Group. (1993). Study protocol for the World Health Organisation project to develop a quality of life assessment instrument (WHOQOL). Quality of Life Research, 2, 153–159. Hambleton, R. K., & Patsula, L. (1999). Increasing the validity of adapted tests: Myths to be avoided and guidelines for improving test adaptation practices. Journal of Applied Testing Technology, 1, 1–30. International Test Commission Guidelines for Translating and Adapting Tests version. (2010). http://www.intestcom.org. Cronbach, J. L. (1951). Coefficient alpha and internal structure of tests. Psychometrika, 16, 297–334.
Psychometric properties of KIDSCREEN health-related quality of life questionnaire in Iranian adolescents Ahmad Shahabeddin Parizi • Gholamreza Garmaroudi Mojtaba Fazel • Sepideh Omidvari • Seyed Ali Azin • Ali Montazeri • Saba Jafarpour
•
Accepted: 19 February 2014 Ó Springer International Publishing Switzerland 2014
Abstract Introduction Health-related quality of life (HRQOL), which is receiving increasing attention, is a multidimensional concept that encompasses different areas including the physiological, psychological, social, and spiritual aspects of life. The KIDSCREEN-52 questionnaire is designed to measure the HRQOL of 8–18-year-old children and adolescents. The aim of this study was to develop a Persian version of KIDSCREEN-52 and analyze the validity and reliability of the translated version. Method The KIDSCREEN-52 was translated into Persian in keeping with the international cross-cultural translation guidelines. A cross-sectional study was performed in the city of Tehran during 2012–2013. 328 students ranging in age from 8 to 18 years were enrolled in the study. The reliability for each dimension was estimated using Cronbach’s alpha coefficient. To examine the validity of the A. S. Parizi School of Public Health, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] G. Garmaroudi (&) Department of Health Promotion and Education, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected] M. Fazel Department of Pediatrics, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected]
questionnaire, a confirmatory factor analysis (CFA) was conducted. Results The Cronbach’s alpha coefficient was higher than 0.7 in all ten dimensions except self-perception. Validity of this questionnaire was confirmed by CFA. (Relative chi square (v2/df) = 1.73; root-mean-square error of approximation = 0.047; normed fit index = 0.93; Tucker–Lewis index = 0.97; comparative fit index = 0.97; and relative fit index = 0.92.) Conclusion The Persian version of KIDSCREEN-52 is reliable and valid and can be used as a self-administered instrument for measuring HRQOL in children and adolescents in Iran. Keywords Health-related quality of life KIDSCREEN Adolescents Validity
A. Montazeri e-mail: [email protected] S. A. Azin Reproductive Infections Research Group, Avecina Research Institute, ACECR, Tehran, Iran e-mail: [email protected] S. Jafarpour Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran e-mail: [email protected]
S. Omidvari A. Montazeri Menal Health Research Department, Health Metrics Research Center, Iranian Institute for Health Sciences Research, ACECR, Tehran, Iran e-mail: [email protected]
123
Qual Life Res
Background
Table 1 Internal consistency of KIDSCREEN-52 in 13 European countries survey
Quality of life is a key concept in the health and medical professions. It is a subjective perception of well-being that varies between different individuals [1]. Health-related quality of life (HRQOL), which is receiving increasing attention, is a multidimensional concept that encompasses different areas including the physiological, psychological, social, and spiritual aspects of life [1–6]. This concept is closely related to WHO’s definition of health: ‘‘a state of complete physical, mental, and social wellbeing and not merely the absence of disease or infirmity’’ [7]. HRQOL used to be assessed mainly among adults, but in recent years increasing attention has been given to the assessment of HRQOL in children and adolescents [1, 8, 9]. Developing an appropriate instrument is vital for monitoring HRQOL. Tools designed for adults are not suitable for assessing HRQOL in children [1, 10]. Children’s emotions, cognitive development, and reading skills should be considered [1, 3, 9], and specific aspects of their lives including their relations with family, friends, and school must be taken into account [4]. By using the properly designed instrument, children and adolescent can reliably answer the HRQOL questionnaires and can therefore be assessed directly instead of according to the data provided by their mother or primary care giver [3, 11]. There are over a hundred instruments available for assessing HRQOL in children and adolescents [4]. Because the sense of wellbeing and being functional can be affected by cultural backgrounds, the measuring tool should be developed simultaneously among different cultures, or the existing accepted instrument should be translated, analyzed, and adapted into other languages considering the cultural diversities [12]. KIDSCREEN-52 is a psychometric sound health-related quality of life measure that was developed in the KIDSCREEN project conducted in 2001–2004 by Ravens-Sieberer et al. It is a self-report measure that assesses the HRQOL in both healthy and chronically ill children aged 8–18 years. It measures ten HRQOL dimensions: physical well-being, psychological well-being, moods and emotions, self-perception, autonomy, parent relations and home life, social support and peers, school environment, social acceptance (bullying), and financial resources. The project was conducted by the study center at Robert Koch Institute in Berlin, Germany together with twelve European countries, including Austria, Czech Republic, France, Greece, Hungary, Ireland, Poland, The Netherlands, Spain, Sweden, Switzerland, and United Kingdom. As a result of the simultaneous development in thirteen different countries, KIDSCREEN questionnaires are cross-national instruments [9]. Several other versions of KIDSCREEN are also available, including Norwegian [1], Korean [3], Argentinean [4], Serbian [12] and Turkish [15].
Dimension
No. items
Cronbach’s a
Physical well-being
5
0.80
123
Psychological well-being
6
0.89
Moods and emotions
7
0.85
Self-perception
5
0.79
Autonomy
5
0.84
Parent relation and home life
6
0.88
Financial resources Social support and peers
3 6
0.89 0.84
School environment
6
0.87
Social acceptance/bullying
3
0.77
The aim of this study was to develop a Persian version of KIDSCREEN-52 HRQOL and analyze the validity and reliability of the translated version.
Methods Sample and data collection As a rule of thumb, the number of samples to validate a questionnaire varies from 4 to 10 subjects per variable [16]. It is also recommended that choosing a minimum 300 subject for a study is acceptable [17]. KIDSCREEN-52 is a questionnaire with 52 items, so a sample size with 300 subjects was chosen. This cross-sectional study was performed in the city of Tehran during 2012–2013. The eligible population for the study was all male and female children aged 8–18 years attending schools in Tehran. Schools in Iran are single sex. School education is divided into the following cycles: preschool (1 year cycle, children aged 5); Primary (6 year cycle, children aged 6–11); Middle (2 year cycle, students aged 12–13); High school (4 year cycle, students aged 14–18). Students of the third grade of primary school through fourth grade of high school (a total of ten grades) were eligible to enter the study. Tehran’s municipality has divided the city into 22 regions by the geographic location on the map. In this study, these regions were stratified by district into 5 strata (North, Center, South, West, and East). In each stratum, the schools were divided into two groups: girls’ schools and boys’ schools. Then, from each of these groups, one primary, one middle, and one high school were selected randomly; that made a sum of 6 schools in each stratum and a total of 30 schools in the study. In each grade 3, students were randomly chosen to enter the study. As a result, considering the ten eligible
Qual Life Res
grades, the total number of students enrolled in the study was at least 300. Schools that did not agree to participate were replaced by another randomly selected school from the same group in the stratum. Before performing the study, an approval was obtained from the ethical review committee of Tehran University of Medical Sciences. In each school, the students and their parents were given some information about the study, reassured that the given information would remain confidential, and written consent was obtained from the parents. Only those students whose parents had consented to their joining the study were included. The self-report instrument KIDSCREEN-52 HRQOL was given to the participants while an instructor was present.
Instrument The KIDSCREEN-52 questionnaire includes 52 items which are distributed among ten dimensions including physical well-being (5 items), psychological well-being (6 items), moods and emotions (7 items), self-perception (5 items), autonomy (5 items), parent relations and home life (6 items), financial resources (3 items), social support and peers (6 items), school environment (6 items), and social acceptance/bullying (3 items). Questions should be answered based on attitudes, moods, feelings, and behaviors in the previous week, and the items follow a 5-point Likert-type scale [18] with three different type of responses: (1) excellent, very good, good, fair, poor; (2) extremely, very moderately, slightly, not at all; (3) always, very often, quite often, seldom, never. Items which were negatively formulated were re-coded according to the manual handbook of KIDSCREEN [19]. Finally, the score of each dimension was transformed linearly to a 0–100-point scale. The reliability of the KIDSCREEN-52 questionnaire was perused in 13 European countries at 2007 [18], and the results are presented in Table 1. The KIDSCREEN-52 was translated into Persian according to international cross-cultural translation guidelines [20] and using the forward–backward–forward technique [21]: two independent translators who had Persian as their mother language translated the English version into Persian; these translations were assessed and compared by a group of experts, and the best translation was chosen for each item. Because the age range of the intended population group of this questionnaire is wide (from 8 to 18), the simplest and most familiar words and phrases were chosen [22]. This mixed translation was reverted to English by another professional translator. This version was sent to the KIDSCREEN committee and, after further confirmation by this committee; the mixed Persian version was used in this study.
Table 2 Internal consistency of Persian KIDSCREEN-52 Dimension
Mean (SD)
No. items
Cronbach’s a
Physical well-being
66.997 (21.688)
5
0.784
Psychological well-being
66.349 (22.570)
6
0.861
Moods and emotions
64.678 (20.954)
7
0.807
Self-perception
68.338 (20.301)
5
0.601
Autonomy
55.366 (23.965)
5
0.784
Parent relation and home life
68.191 (24.797)
6
0.876
Financial resources
55.919 (29.792)
3
0.841
Social support and peers
54.611 (21.079)
6
0.718
School environment
62.779 (23.171)
6
0.805
Social acceptance/ bullying Total
83.206 (19.848)
3
0.706
64.643 (8.469)
52
0.937
Table 3 Fit indices based on sum of scores of 10 dimensions Indices
Value
Recommended cutoff value
v2/df
1.73
B2
RMSEA
0.047
B0.05
NFI
0.93
C0.90
TLI
0.97
C0.90
CFI
0.97
C0.90
RFI
0.92
C0.90
Statistical analysis We used SPSS for Windows (20.0) for statistical analysis and Lisrel (version 3) for the confirmatory factorial analysis. The reliability of each dimension was estimated using the Cronbach’s alpha coefficient. Alpha coefficients equal to or higher than 0.7 were considered acceptable [23]. To examine the validity of the questionnaire, a confirmatory factor analysis (CFA) was conducted, which provided fitness indices to see how well the model fit the data. There were various recommendations in the literature regarding number, type, and cutoff values for the goodness-of-fit needed to be reported [1]. In this study, we used the following indices: relative chi square (v2/df) and root-meansquare error of approximation (RMSEA) as absolute fit measures and normed fit index (NFI), Tucker–Lewis index (TLI), comparative fit index (CFI), and relative fit index (RFI) as incremental fit measures. The acceptable cutoff point for incremental measures is 0.90. RMSEA values B0.05 and v2/df values B2 are regarded as a close fit. In order to assess the construct validity, item-scale correlation
123
Qual Life Res Table 4 Item-scale correlation coefficient Physical activities and health
Feelings
General mood
About yourself
Free time
Family and home life
Money matters
Friends
School and learning
Bullying
PAHQ1
0.674**
0.431**
0.320**
0.298**
0.219**
0.303**
0.272**
0.077
0.260**
0.185**
PAHQ2
0.764**
0.581**
0.356**
0.323**
0.322**
0.464**
0.255**
0.202**
0.482**
0.101
PAHQ3 PAHQ4
0.755** 0.738**
0.460** 0.384**
0.260** 0.221**
0.260** 0.259**
0.345** 0.263**
0.392** 0.302**
0.283** 0.211**
0.146** 0.172**
0.307** 0.255**
0.144** 0.123*
PAHQ5
0.730**
0.587**
0.330**
0.297**
0.310**
0.370**
0.195**
0.239**
0.467**
0.159**
FQ1
0.564**
0.826**
0.435**
0.432**
0.439**
0.547**
0.360**
0.169**
0.480**
0.144**
FQ2
0.456**
0.731**
0.452**
0.351**
0.335**
0.454**
0.262**
0.236**
0.454**
0.151**
FQ3
0.474**
0.798**
0.452**
0.427**
0.402**
0.487**
0.357**
0.152**
0.519**
0.209**
FQ4
0.511**
0.720**
0.380**
0.433**
0.424**
0.405**
0.305**
0.139*
0.435**
0.048
FQ5
0.561**
0.780**
0.365**
0.364**
0.365**
0.452**
0.238**
0.172**
0.432**
0.145**
FQ6
0.509**
0.762**
0.338**
0.301**
0.444**
0.450**
0.277**
0.313**
0.476**
0.174**
GMQ1
0.134*
0.196**
0.546**
0.210**
0.044
0.104
0.005
0.158**
0.110*
GMQ2
0.309**
0.396**
0.750**
0.394**
0.238**
0.326**
0.216**
0.102
0.253**
0.098
GMQ3
0.242**
0.290**
0.685**
0.259**
0.178**
0.271**
0.079
0.040
0.222**
0.066
GMQ4
0.316**
0.433**
0.735**
0.435**
0.237**
0.427**
0.249**
0.065
0.318**
0.187**
GMQ5
0.236**
0.328**
0.626**
0.273**
0.145**
0.277**
0.132*
-0.013
0.228**
0.065
GMQ6
0.331**
0.434**
0.725**
0.460**
0.209**
0.393**
0.236**
-0.047
0.285**
0.140*
GMQ7 AYQ1
0.335** 0.384**
0.408** 0.472**
0.694** 0.347**
0.434** 0.492**
0.304** 0.365**
0.356** 0.415**
0.296** 0.311**
0.076 0.120*
0.238** 0.362**
0.271** 0.122*
AYQ2
0.366**
0.556**
0.341**
0.598**
0.403**
0.556**
0.439**
0.179**
0.492**
0.205**
AYQ3
0.134*
0.191**
0.375**
0.660**
0.090
0.205**
0.231**
-0.009
0.110*
0.106
AYQ4
0.131*
0.128*
0.251**
0.644**
0.017
0.187**
0.109*
-0.073
0.163**
0.189**
AYQ5
0.213**
0.224**
0.313**
0.700**
0.177**
0.315**
0.084
0.023
0.230**
0.134*
FTQ1
0.282**
0.423**
0.185**
0.293**
0.747**
0.443**
0.395**
0.286**
0.292**
0.055
FTQ2
0.331**
0.436**
0.260**
0.295**
0.759**
0.446**
0.446**
0.303**
0.355**
0.068
FTQ3
0.303**
0.365**
0.171**
0.212**
0.796**
0.331**
0.426**
0.360**
0.230**
0.100
FTQ4
0.189**
0.254**
0.168**
0.129*
0.643**
0.262**
0.249**
0.422**
0.108
0.078
FTQ5
0.355**
0.427**
0.270**
0.300**
0.717**
0.442**
0.356**
0.282**
0.407**
0.071
FHLQ1
0.385**
0.451**
0.404**
0.430**
0.402**
0.802**
0.422**
0.225**
0.423**
0.232**
FHLQ2
0.366**
0.423**
0.290**
0.413**
0.310**
0.740**
0.383**
0.196**
0.525**
0.102
FHLQ3
0.464**
0.593**
0.385**
0.466**
0.513**
0.805**
0.438**
0.246**
0.472**
0.224**
FHLQ4
0.381**
0.534**
0.409**
0.461**
0.513**
0.820**
0.409**
0.316**
0.519**
0.235**
FHLQ5
0.414**
0.434**
0.361**
0.469**
0.366**
0.774**
0.378**
0.231**
0.462**
0.179**
FHLQ6 MMQ1
0.354** 0.291**
0.433** 0.336**
0.312** 0.188**
0.314** 0.330**
0.381** 0.487**
0.778** 0.437**
0.282** 0.892**
0.249** 0.265**
0.428** 0.313**
0.113* 0.201**
MMQ2
0.318**
0.378**
0.296**
0.384**
0.452**
0.486**
0.885**
0.289**
0.384**
0.154**
MMQ3
0.257**
0.304**
0.163**
0.253**
0.397**
0.349**
0.835**
0.326**
0.269**
0.136*
FrQ1
0.184**
0.268**
0.134*
0.089
0.435**
0.294**
0.300**
0.649**
0.241**
0.099
FrQ2
0.076
-0.110*
-0.164**
0.150**
0.153**
0.548**
0.007
0.118*
FrQ3
0.174**
0.193**
0.033
0.084
0.378**
0.303**
0.308**
0.715**
0.249**
0.124*
FrQ4
0.283**
0.290**
0.086
0.186**
0.315**
0.318**
0.196**
0.637**
0.388**
0.076
FrQ5
0.090
0.124*
-0.008
0.076
0.201**
0.156**
0.161**
0.626**
0.199**
0.002
FrQ6
0.089
0.153**
0.056
0.043
0.289**
0.178**
0.200**
0.705**
0.210**
0.016
SLQ1
0.368**
0.483**
0.268**
0.336**
0.283**
0.448**
0.216**
0.229**
0.767**
0.028
SLQ2
0.419**
0.481**
0.255**
0.359**
0.238**
0.447**
0.330**
0.170**
0.675**
0.146**
SLQ3
0.352**
0.477**
0.265**
0.346**
0.326**
0.426**
0.235**
0.227**
0.751**
0.048
SLQ4
0.386**
0.371**
0.247**
0.200**
0.283**
0.437**
0.323**
0.289**
0.565**
0.150**
123
-0.012
-0.018
-0.062
Qual Life Res Table 4 continued Physical activities and health
Feelings
General mood
About yourself
Free time
Family and home life
Money matters
Friends
School and learning
Bullying
-0.001
SLQ5
0.250**
0.327**
0.264**
0.268**
0.185**
0.354**
0.116*
0.179**
0.742**
SLQ6
0.306**
0.462**
0.241**
0.338**
0.316**
0.451**
0.376**
0.312**
0.756**
0.046
BQ1
0.108
0.090
0.145**
0.152**
0.083
0.041
0.029
0.038
0.747**
BQ2
0.170**
0.171**
0.159**
0.201**
0.115*
0.216**
0.175**
0.088
0.045
0.836**
BQ3
0.182**
0.188**
0.172**
0.220**
0.140*
0.244**
0.227**
0.146**
0.141*
0.797**
-0.020
* Correlation is significant at the 0.05 level (2-tailed). ** Correlation is significant at the 0.01 level (2-tailed)
coefficients were calculated. Construct validity was assumed if items showed the highest correlation with their original dimension.
Results 328 students were enrolled in the study. Of a total of 328 participants, 49.4 % were male and 50.6 % were female. Mean age of the participants was 12.9 ± 2.9, ranging from 8 to 18 years. Average scores of the 10 KIDSCREEN-52 dimensions along with Cronbach’s alpha coefficients are presented in Table 2. The means and SDs are shown in transformed metric scale ranging from 0 to 100. The Cronbach’s alpha coefficient is higher than 0.7 in all ten dimensions except self-perception, which is 0.601 (Table 2). Table 3 presents the CFA based on the sum scores of ten dimensions. The chi-square test of the model was statistically significant (df = 1,179, p value \0.001). Each items in the Persian KIDSCREEN correlated significantly higher to the dimension to which it was categorized than to the other nine dimensions. This can be interpreted as a good construct validity of the questionnaire (Table 4).
dimension could be acceptable. In a similar study, the alpha coefficient of less than 0.7 in two different dimensions was considered good enough for a measure that was developed for a different population [4]. Recently, CFA is increasingly used to examine the validity of the quality of life questionnaires, which provides fitness indices to see how well the model fit the data [6]. In our study, construct validity was assessed by CFA. The chi-square test was significant. Relative chi square was less than the recommended cutoff value. CFI, TLI, NFI, and RFI were above 0.90 and RMSEA was less than 0.05, confirming the construct validity of all dimensions. The main strengths of this study were the adequate sample size and random selection of subjects from different districts with diverse ethnical groups and socioeconomic levels that can be a good representative of the entire country. The limitation of our study was that the cross-sectional design did not provide information about probable changes in HRQOL in children over time. Further prospective studies should be carried out to investigate these changes. In conclusion, the Persian version of KIDSCREEN-52 is a reliable and valid measure adopted into the Persian language, which considers the cultural context and ethnical diversities. The questionnaire can be used as a self-administered instrument for measuring HRQOL in children and adolescents in Iran.
Discussion KIDSCREEN-52 is a self-report questionnaire that assesses the HRQOL in children aged 8–18 years and was developed in the KIDSCREEN project conducted by RavensSieberer et al. The aim of this study was to develop a Persian version of KIDSCREEN-52 considering the Iranian cultural background and to examine the validity and reliability of the adopted questionnaire. Internal consistency reliability of the KIDSCREEN questionnaire had an above-satisfactory cutoff value of 0.7 in all dimensions except for ‘‘About yourself’’. Considering the fact that the KIDSCREEN-52 was developed in European countries with different languages and cultural bases and that selfperception is not clearly discussed in Iranian culture in families or during pre-school education, the reliability of this
References 1. Haraldstad, K., Christophersen, K. A., Eidea, H., Nativgc, G. K., Helsetha, S., & The KIDSCREEN group Europe. (2011). Health related quality of life in children and adolescents: Reliability and validity of the Norwegian version of KIDSCREEN-52 questionnaire, a cross sectional study. International Journal of Nursing Studies, 48(5), 573–581. 2. Robitail, S., Sime´oni, M. C., Ravens-Sieberer, U., et al. (2007). Children proxies’ quality-of-life agreement depended on the country using the European KIDSCREEN-52 questionnaire. Journal of Clinical Epidemiology, 60(5), 469–478. 3. Hong, S. D., Yang, J. W., Jang, W. S., Byun, H., Lee, M. S., Kim, H. S., et al. (2007). The KIDSCREEN-52 Quality of life measure for children and adolescents (KIDSCREEN-52-HRQOL): Reliability and validity of the Korean version. Journal of Korean Medical Science, 22(3), 446–452.
123
Qual Life Res 4. Berra, S., Tebe´c, C., Esandie, M. E., & Carignanog, C. (2013). Reliability and validity of the KIDSCREEN-52 questionnaire to measure health related quality of life in the 8 to 18 year-old Argentinean population. Archivos Argentinos de Pediatrı´a, 111(1), 29–35. 5. Bullinger, M., Schmidt, S., & Petersen, C. (2002). DISABKIDS Group. Assessing quality of life of children with chronic health conditions and disabilities a European approach. International Journal of Rehabilitation Research, 25(3), 197–206. 6. Fayersm, P. M., & Machin, D. (2007). Quality of life. The assessment, analysis and interpretation of patient-reported outcomes (2nd ed.). London: Wiley. 7. Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference, New York, 19–22 June, 1946; signed on 22 July 1946 by the representatives of 61 States (Official Records of the World Health Organization, No. 2, p. 100) and entered into force on 7 April 1948. http://www. who.int/about/definition/en/print.html. 8. Tzavara, C., Tzonou, A., Zervas, I., & Tountas, Y. (2012). Reliability and validity of the KIDSCREEN-52 health related quality of life questionnaire in a Greek adolescent population. Annals of General Psychiatry, 11, 3. 9. Ravens-Sieberer, U., Gosch, A., Rajmil, L., et al. (2005). KIDSCREEN-52 quality-of-life measure for children and adolescents. Expert Review of Pharmacoeconomics and Outcomes Research, 5, 353–364. 10. Huebner, E. S., Valois, R. F., Suldo, S. M., Smith, L., McKnight, C., Seligson, J. L., et al. (2004). Perceived quality of life: A neglected component of adolescent health assessment and intervention. Journal of Adolescent Health, 34(4), 270–278. 11. Riley, A. W. (2004). Evidence that school-age children can selfreport on their health. Ambulatory Pediatrics, 4, 371–376. 12. Stevanovic, D., Tadic, I., Novakovic, T., Kisic-Tepavcevic, D., & Ravens-Sieberer, U. (2012). Evaluation the Serbian version of the KIDSCREEN quality-of-life questionnaires: Reliability, validity, and agreement between children’s and parents’ ratings. Quality of Life Research, 22, 1729–1737 13. Mazur, J. (2004). Development and initial psychometric analysis of the generic quality of life questionnaire for Polish children and
123
14.
15.
16.
17.
18.
19.
20.
21.
22. 23.
adolescents (KIDSCREEN-52). Medycyna Wieku Rozwojowego, 8(3 Pt 1), 513–533. Tebe, C., Berra, S., Herdman, M., et al. (2008). Reliability and validity of the Spanish version of the KIDSCREEN-52 for child and adolescent population. Medicina Clı´nica (Barc), 130(17), 650–654. Meral, B. F., & Fidan, A. (2013). The examination of psychometric properties of KIDSCREEN-short version on children with autism in Turkey. International Journal on New Trends in Education and their Implications, 4(2), 151–159. Vet, H. C. W., Ader, H. J., Terwee, C. B., & Pouwer, F. (2005). Are factor analytical techniques used appropriately in the validation of health status questionnaires? A systematic review on the quality of factor analysis of the SF-36. Quality of Life Research, 14, 1203–1218. Rouquette, A., & Falissard, B. (2011). Sample size requirements for the internal validation of psychiatric scales. International Journal of Methods in Psychiatric Research, 20, 235–249. Ravens-Sieberer, U., Gosch, A., Rajmil, L., Erhart, M., Bruil, J., Power, M., et al. (2008). The KIDSCREEN-52 quality of life measure for children and adolescents: Psychometric results from a Cross-Cultural Survey in 13 European countries. Value in Health, 11, 645–658. The KIDSCREEN Group Europe. (2006). The KIDSCREEN questionnaires quality of life questionnaires for children and adolescents Handbook. Lengerich: Pabst Science Publishers. WHOQOL Group. (1993). Study protocol for the World Health Organisation project to develop a quality of life assessment instrument (WHOQOL). Quality of Life Research, 2, 153–159. Hambleton, R. K., & Patsula, L. (1999). Increasing the validity of adapted tests: Myths to be avoided and guidelines for improving test adaptation practices. Journal of Applied Testing Technology, 1, 1–30. International Test Commission Guidelines for Translating and Adapting Tests version. (2010). http://www.intestcom.org. Cronbach, J. L. (1951). Coefficient alpha and internal structure of tests. Psychometrika, 16, 297–334.
