Validity
Convergent validity (convergent construct validity testing a pre-defined hypothesis) was assessed by determining the extent to which scores on a PRO under development correlate with PGIS and FACT-An, which measure the same or related constructs, with strong relationships expected. In contrast, discriminant validity was assessed by determining relationships between PKDD and PKDIA scores and EQ-5D-5L, and MCS-12 and PCS-12 from the SF-12v2, which are thought to be unrelated to the constructs measured by the PKDD and PKDIA, with weak relationships expected. Convergent and discriminant validity were assessed using Spearman correlations. Cohen’s interpretation of r as an effect size was also employed, with correlation coefficients interpreted as small (0.1 ≤|r|), medium (0.3 ≤|r|) or large (0.5 ≤|r|) [Known-groups validity was assessed to evaluate the ability of the PKDD and PKDIA to discriminate between distinct groups when a difference between them is expected and was assessed using a linear model and PKDD and PKDIA data at baseline, with known-groups defined by baseline PGIS score.