The ICECAP-A instrument for capabilities: assessment of construct validity and test-retest reliability in a general Dutch population

Purpose The ICEpop CAPability measure for Adults (ICECAP-A) assesses five capabilities that are important to one’s well-being. The instrument might be an important addition to generic health questionnaires when evaluating quality of life extending beyond health. This study aimed to conduct a psychometric assessment of the Dutch translation of the ICECAP-A. Methods Construct validity of the instrument was assessed in two ways. First, by measuring correlations with the EQ-5D-5L questionnaire and a measure of self-efficacy and, second, by investigating the ability to distinguish between groups known to differ on the construct the ICECAP-A means to capture. Additionally, test–retest reliability was evaluated. Results In total, 1002 participants representative of the general Dutch population completed an online survey. For test–retest reliability, 252 participants completed the same questionnaire 2 weeks later. The ICECAP-A indicated moderate to strong correlations with the EQ-5D-5L and a strong correlation with self-efficacy. Furthermore, it was capable of differentiating known groups. Moreover, results indicated adequate test–retest reliability with an intraclass correlation coefficient of 0.79. Conclusion In summary, results suggest adequate test–retest reliability and construct validity and indicate that the ICECAP-A might be of added value, especially when considering areas outside of the traditional health intervention model.