Development of a self-report measure of cognitive change: assessment of interpretability in two samples, people with HIV and people without HIV

Aim: The overall aim of this study was to develop a method of measuring change in cognitive ability from the person's perspective.

Methods: Cognitive change items came from an item pool that was used to develop the Communicating Cognitive Concerns Questionnaire (C3Q). The change items were administered to a test sample of 211 people with HIV + and a sample of 484 people drawn from the general population (HIV- sample). Rasch analysis was used to identify items that formed a linear continuum and correlations with measures of related constructs were used to support the interpretability of the new measure.

Results: Eleven of the original 12 change items fit the unidimensional Rasch model in both samples with a near similar ordering of the items. The average value for cognitive change of the HIV + sample was greater than that of the HIV- sample. Values on C3Q-Change correlated most highly (> 0.7) with current self-reported cognitive status and measures of depression and anxiety (> 0.6). The lowest correlation was with performance-based cognitive ability (r = 0.2).

Conclusion: The items of C3Q-Change fit a strong measurement model and related to converging constructs in an expected way. Further work needs to be done to assess the meaning of self-reported cognitive change in relationship to measured change and to examine sources of differential item functioning.