Anchor-based methods for assessing meaningful change
COMPLICATIONS
Anchor-based methods were conducted to establish the level of change which could be considered meaningful for the domains. For this analysis, both PIB weekly mean and PIB weekly maximum scores were assessed alongside the Decision Tree score. The anchor-based analyses were performed in the psychometric analysis population using data from Visit 1 and Visit 2. The suitability of proposed anchors was tested using a polyserial correlation coefficient to establish the relationship between the anchor categories and change in domain scores. Anchors with correlations of For PIB weekly mean and PIB weekly maximum, PGIC was the only anchor demonstrating a sufficient polyserial correlation coefficient. Thus, the PGIC anchor was used to define groups of patients who had experienced improvement or no change. For the Decision Tree score, the CGIS anchor was used instead due to a sufficient polyserial correlation coefficient, and patient groups were again defined as experiencing either improvement or no change. Subjects with worsened skin complications were excluded from this analysis. The groupings based on the PGIC/CGIS anchor were as follows: ‘Improved’ (very much improved, much improved, or a little improved at Visit 2) and ‘Stable’ (no change at Visit 2).The within-group mean change scores evaluated the minimal important change (MIC) within groups. The mean change in domain score was calculated for patients classified according to the PGIC anchor (PIB weekly mean and PIB weekly maximum) and the CGIS anchor (Decision Tree score). The MIC estimate was derived using each groups’ mean change scores.The between-group differences in mean change scores evaluated the minimal important difference (MID) between groups. This analysis informed between-group MID estimates, and the mean change in domain scores was calculated for patients classified as above according to the PGIC anchor (PIB weekly mean and PIB weekly maximum) and the CGIS anchor (Decision Tree score). The MID estimate was defined as the difference in mean change score between these groups.