Assessing health-related quality of life in adolescents: some psychometric properties of the first Norwegian version of KINDL

The study presented in this paper is part of a larger Norwegian investigation among adolescents, where the overall aim is to develop methods to promote their quality of life (QoL), to discover risk factors or threats to adolescents' well-being, and finally to prevent the negative effects of such factors. An adequate generic health-related quality of life (HR-QoL) measure is therefore needed. However, only a limited number of well validated instruments that measure HR-QoL in adolescents exist, and to date only a few has been translated into Norwegian. The purpose of this study was therefore to examine some psychometric properties of the first Norwegian version of a simple, generic, German HR-QoL questionnaire for adolescents, KINDL. The instrument consists of 24-items, distributed in six subscales, which correspond to six domains of adolescents' HR-QoL. Based on a sample of 239 healthy adolescents, the internal consistency reliability is satisfactory for both the total scale and the subscales of 'Self-esteem and Family', fairly good for the 'Emotional' subscale, but lower for the subscales 'Physical', 'Friends' and 'School'. Factor analyses, which concerns construct validity, yielded interpretable solutions. The factor solutions at item level were interpreted to be in line with the original subscales, while factor analysis at subscale level indicated that a common QoL core is involved. To conclude, the Norwegian version of KINDL appears, in general, to be a psychometrically acceptable method of measuring HR-QoL in healthy adolescents. However, the alpha-values of some of the subscales are not optimal, and these scales should be used with caution in research and profession. Still KINDL-N is considered suitable for screening purposes in the public health area and especially within school-health care.