Validation of a Mobile Application Version of the Cognition Kit Digit Symbol Substitution Test in Patients With Major Depressive Disorder

Objective: The primary objective of this study was to evaluate the convergent validity of the Cognition Kit Digit Symbol Substitution Test (DSST) mobile app among patients with major depressive disorder (MDD), compared to the gold-standard paper Pearson WAIS IV DSST. Secondarily, patient satisfaction with the mobile app was assessed.

Methods: Adults (n=30) ages 18 to 65 (mean=42, SD=13; 40% male), all experiencing a moderate-severe major depressive episode (Montgomery-Åsberg Depression Rating Scale score ≥ 20), participated in this study by completing a paper DSST and the mobile app DSST at both visits 1 and 2; visits were 1 week apart. A 10-item app satisfaction survey was administered during visit 2 and scored using a 5-point Likert satisfaction scale. Pearson correlations were calculated to evaluate convergent validity of the mobile app and the paper DSST.

Results: Pearson correlation analyses showed significant positive correlations between the paper DSST and the mobile app at both visits (visit1: r=0.69, p < 0.001; visit2: r=0.82, p < 0.001). Additionally, significant positive correlations were found between scores on the paper DSST between visits1 and 2 (r=0.92, p < 0.001) and between scores on the mobile app between visits 1 and 2 (r=0.75, p < 0.001). A majority of participants “agreed” or “strongly agreed” that the mobile app was user-friendly/easy to use (87%) and “preferred” the mobile app to the paper version (57%).

Conclusions: This study demonstrated that the Cognition Kit DSST mobile app is a valid and accessible alternative to the paper DSST for measuring cognitive functioning in adults with MDD.