Xuxi Zhang

physical domain of the TFI and less the other 2 domains. We hypothesized that the SF ‐ 12 MCS and MHI ‐ 5 strongly relate to the psychological domain of the TFI and less the other 2. We also hypothesized that the short ‐ JG strongly relates to the social domain of the TFI and less to the other 2. The convergent and divergent validity were assessed using Pearson correlation coefficients. 12 A statistically significant correlation between a domain score and the score of an alternative measure of the same domain was considered as a satisfactory convergent validity; with a higher correlation indicating a better validity. 12, 15, 22 Divergent validity was assumed if each alternative measure had a higher correlation with the corresponding domain of the TFI, but a lower correlation with the each of the other domains of the TFI. 12, 15, 22 To examine the concurrent validity, we used the following alternative measures as the criterion: (1) SHARE ‐ FI, (2) GARS and (3) GALI (physical domain), (4) MHI ‐ 5 (psychological domain) and (5) short ‐ JG (social domain). The concurrent validity was assessed using the receiver operating characteristic (ROC) curve analysis. 12, 22 Accuracy was measured by the area under the ROC curve (AUC). An AUC between 0.7 and 0.8 was considered acceptable, between 0.8 and 0.9 excellent and an AUC of more than 0.9 was considered outstanding. 35 The Youden index (sensitivity + specificity  ‐  1) was adopted as the criterion for selecting the optimum cut ‐ off point(s). 36 All analyses were conducted among the total population as well as by country. All analyses were performed with SPSS v 23.0 (IBM SPSS Statistics for Windows, Armonk, NY). The level of significance was P ‐ value <0.05. RESULTS Participant Characteristics Table 1 presents the general characteristics of the total population and by country. The mean age of the total population was 79.7 (standard deviation = 5.7) years and 60.3% were women. Participants from Spain and Greece were younger, had less often completed secondary education and less often lived alone than other countries ( P < .001). Participants from Croatia have higher physical and social domain scores than other countries, and participants from Greece have higher psychological domain scores ( P < .001). Scoring Distributions Table 2 presents the score distributions the TFI. A floor effect (>25% of the respondents had the lowest possible score 37 ) was observed in the physical (the Netherlands), psychological (the total population, Spain, the Netherlands and the UK) and social (the total population and each country except Croatia) domains. 82 Chapter 4