Original Articles

By Dr. Dejan Stevanovic
Corresponding Author Dr. Dejan Stevanovic
Psychiatry, General Hospital Sombor, -
Submitting Author Dr. Dejan Stevanovic

KINDL, questionnaire, quality of life, children, adolescents

Stevanovic D. KINDL Quality Of Life Questionnaire In Serbia: Referent Values For Healthy Children And Adolescents. WebmedCentral PAEDIATRICS 2010;1(12):WMC001342
doi: 10.9754/journal.wmc.2010.001342
Submitted on: 11 Dec 2010 04:55:12 PM GMT
Published on: 13 Dec 2010 02:48:27 PM GMT


The objective of this report was to present the referent values of the Serbian KINDL for healthy children and adolescents. The data from 756 children and adolescents and 618 parents were used. The mean values with standard deviations, 95% confidence intervals, and percentiles were calculated for KINDL. Additionally, the differences between genders, children and parents, and the correlations of age with the KINDL scores were given. The mean values of the subscales ranged 59.51 – 76.39 for the children and 68.96 – 79.97 for the parents. The total scores were 76.29 and 79.86, respectfully. Between the male and female subjects, no significant differences were observed. However, the majority of the scores significantly, but inversely, correlated with age. The referent values were given for gender and age.


The KINDL, a generic quality of life (QOL) questionnaire, is frequently used to evaluate everyday living in children and adolescents [1, 2]. This measure considers QOL as a psychological construct including physical, psychosocial, and functional aspects of well-being and daily functioning [3]. From measurement perspectives, the KINDL provide reliable and valid QOL assessments in screening or evaluative purposes [2].
The KINDL was translated into Serbian and psychometrically validated during 2005/06. Three validation studies were organized in order to evaluate measurement properties of the version in the general populations – a basic psychometric, replication and confirmatory factor analysis study [4, 5]. In the current projects, the KINDL is being evaluated in populations with chronic illnesses/conditions.
The objective of this report was to present the referent values of the Serbian KINDL for healthy children and adolescents.


KINDL questionnaire
The Serbian KINDL questionnaire (KINDL – S) is developed in two forms – Kid-KINDL (8–12 year-olds) and Kiddo-KINDL (13–16 year-olds), both as a self-report and parent questionnaire [4]. Twenty-four items are classified into six sub-scales: Physical well-being – PW, Emotional well-being – EW, Self-esteem – SE, Family – FAM, Friends – FRI, and School – SC. All items are five-Likert-scaled, 1 = never to 5 = all the time. The total subscale score is created as the mean value of all answered items in that scale, while the total KINDL is the mean value of all answered items. The scores are transformed into a 0–100 scale, with the higher the value, the better QOL is. The parent version represents an equivalent to the self-report.
The Serbian KINDL possesses satisfactory measurement characteristics as a screening QOL questionnaire [4]. It is a feasible measure with appropriate face and content validity. The internal consistency coefficients ranged 0.45–0.74 for the subscales and it was above 0.8 for the total, while the reliability in the form of measurement stability is satisfactory for almost all scores (above 0.6) [5]. However, although the discriminative validity of the subscales is appropriate, they are overlapped substantially and the construct validity is not supported [5]. Additionally, the KINDL parent form possesses better measurement properties than the self-report (D. Stevanovic, unpublished results). Following these findings, it is suggested to consider the subscales for preliminary decisions and/or subjects sorting, while the total KINDL score could be used for comparative purposes, mainly for the screening assessments of QOL. Details about the questionnaire will be obtained in the Serbian KINDL manual that is in preparation.
The total number of healthy children/adolescents and their parents from three studies who completed the KINDL was 756 and 618, respectfully. The children and adolescents were randomly recruited and the representativeness was ensured in the way of the subjects’ recruitment from the urban areas of Belgrade to the mid-urban and rural societies of Western Vojvodina, Odzaci. The mean age was 12.34 ± 1.84 years, range 8-16, and 385 were males. For the detailed description of the samples, the reader is referred to the primary references [4, 5].
Statistical analysis
The mean values (M), standard deviations (SD), 95% confidence intervals (CI), percentiles (25, 50, 75), and floor and ceiling effects were calculated for the subscale and total KINDL score [6].
Considering the skewness of the data reported in the first study [4], one-sample Kolmogorov-Smirnov test was run to confirming the significant violation of the normal distribution for the sample (p < 0.001). Consequently, Mann-Whitney test was used to evaluate the differences between gender and between children and parents, while Spearman's rho coefficient was used to evaluate the correlations of age and the KINDL scores. Internal consistency was demonstrated using Cronbach’s α coefficient.
The referent values were given for gender and age. According to age, the referent values were presented so to represent a school grade. The children and parents’ scores were presented separately.


The mean values of the subscales ranged from 59.51 to 76.39 for the children and from 68.96 to 79.97 for the parents. The total scores were 76.29 and 79.86, respectfully. Important ceiling effects were observed for the EW and FAM subscale (Table 1).
Between the male and female subjects, no significant differences were observed in the KINDL scores, as self- or proxy-reported. The majority of the scores significantly, but inversely correlated with age. Finally, Cronbach’s α coefficient ranged from 0.51 to 0.86 (Table 2).
The referent values for gender and age were presented in Table 3 and 4.



The KINDL is a generic pediatric QOL questionnaire validated for the Serbian language. It was culturally adapted and acceptable measurement properties were demonstrated for QOL screening in healthy children and adolescents. The referent values for gender and age provided in this study could be used as a preliminary reference until standardized norms are developed. Up-to-date, only the German and Spanish norms were reported [7, 8].
Several important observations from the study should be considered when using the referent values.
First, although sufficiently large and randomly selected, the subjects from whom the referent values were derived are not necessary representative of gender and age. Notably, the males slightly predominated and the age groups were not equal. Then, the mean values are deferent among the subscales, the range of scores and standard deviations are large, what suggest a broad range for the KINDL scores within “normal limits” [6].
Second, between genders no significant differences were reported in the KINDL scores as self- and/or proxy-reported. Additionally, whilst there was a statistically significant negative correlation between the children age and the self-perceived scores, the correlation coefficient was relatively small to consider the correlation clinically significant. This indicates the KINDL is suitable for using with children over a large age range (8±16 years) without the scores being confounded by the age of the child [6]. However, the effect of age and gender differences on the KINDL should be further explored.
Third, there were significant differences between the children and parents’ KINDL scores, signifying different perceptions of QOL. Differences between children and parents’ QOL evaluations were well documented and this must be followed when selecting who will complete the KINDL and how to use observations [3, 9].
Forth, the internal consistency coefficient of the KINDL varied among the subscales, from 0.51 to 0.73. For the total, it was above 0.8, high enough to suggest the items are looking at the same construct, yet low enough to suggest sufficient variation between the items [6, 10]. Additionally, although the level of internal consistency is acceptable for QOL measures, the data confirmed that the subscales should be only used for preliminary decisions and/or subjects sorting, while the total score could be used confidentially for screening and descriptive purposes [5].
How one should use these referent values? We advise a KINDL evaluator to use the 95% CI and percentiles, although there are other useful methods []. For example, let us say that a 11-year-old healthy boy obtained the total KINDL score of 70 during a screening assessment. From Table 3, this is below the lower end of 95% CI for the entire population and in Table 1 this score is on the 25 percentile. The evaluator therefore should conclude the boy probably has “disturbed” QOL, and depending on occasions, further evaluations should be advised, let us say to screen for the risk factors affecting his QOL or another measure should be used to explore more thoroughly his QOL.


In summary, the KINDL is a useful measure for assessing a child's and/or an adolescent’s quality of life and the referent values provided could be used for different clinical and research purposes, but only screening or descriptive. Additionally, all potential users are advised to follow the above observations and give sufficient priority to the total KINDL score. In incoming projects, the Serbian version will be further evaluated in diverse groups of chronically diseased children and adolescents and fully standardized norms will be developed soon.


QOL - quality of life, KINDL - quality of life measure for children and adolescents


1. Ravens-Sieberer U, Bullinger M. Assessing health-related quality of life in chronically ill children with the German KINDL: First psychometric and content analytical results. Qual Life Res 1998; 7: 399–407.
2. Bullinger M, Brütt AL, Erhart M, Ravens-Sieberer U, BELLA Study Group. Psychometric properties of the KINDL-R questionnaire: results of the BELLA study. Eur Child Adolesc Psychiatr 2008; 17: S125–S32.
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Revision Serbian KINDL reference values
Posted by Dr. Vicky Serra-Sutton on 06 May 2011 02:28:09 PM GMT

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Author's reply Posted by Dr. Dejan Stevanovic on 08 May 2011 01:10:24 PM GMT

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