Treatments trials for apathy in Alzheimer’s disease assess change scores on widely used assessment scales. Here, we aimed to determine whether such change scores on the Neuropsychiatric Inventory - Apathy (NPI-A) scale indicate clinically meaningful change.

Participants completing the Apathy in Dementia Methylphenidate Trial 2 (ADMET 2) were included. Participants in this randomized trial received methylphenidate or placebo for 6- months along with a psychosocial intervention. Assessments included Clinical Global Impression of Change in apathy (CGIC-A) and the NPI-A. Participants in both groups with complete data at the six-month visit were included. CGIC-A was assessed as improved (minimal, moderate or marked), no change, or worsened (minimal, moderate or marked). For CGIC-A levels, mean and standard deviation (SD) of the change in NPI-A from baseline was calculated. Spearman correlation determined the association between change in NPI-A and CGIC-A, and Mann-Whitney U tests determined differences between the ‘no change’ group and the ‘improved’ and ‘worsened’ groups. Effect size (mean NPI-A difference between either ‘improved’ and ‘no change’/ SD of overall change) were calculated. Differences were also assessed at 3 months as a sensitivity analysis.

Overall, 177 participants were included (median age: 77years, Mini Mental State Examination score: 19.3 (4.8), baseline NPI-A [mean, SD]: 7.9, 2.3), change in NPI-A: -3.7 (3.9). On the CGIC-A, 69 were improved, 82 showed no change, and 26 worsened. The Spearman correlation between NPI-A change and CGIC-A was 0.41 (p= 1x 10-8). The change in NPI-A among participants who improved was -5.3 (4.1) [W=1873, p= 3x10-4], among those who worsened was -1.2 (3.1) (W= 1426.5, p= 0.009) compared to those with no change (-3.2 [3.4]),. The NPI-A score for minimal clinical improvement was -4.5 (4.6) with a small effect size of -0.32, which was consistent at 3-months (-0.31).

A minimal clinically significant improvement over 3 and 6-months corresponded to a mean decline of 4.5 points on the NPI-A; however, there is considerable overlap in the NPI-A between levels of clinical impression of change.