Psychometric Properties of the Concise Associated Symptom Tracking Scale and Validation of Clinical Utility in the EMBARC Study

OBJECTIVE: The authors aimed to evaluate psychometric properties of the Concise Associated Symptom Tracking (CAST) Scale and validate the clinical utility of measuring irritability by updating and replicating a previously published outcome calculator from the Combining Medications to Enhance Depression Outcomes (CO‐MED) trial. METHODS: Participants were 292 adults from the Establishing Moderators and Biosignatures of Antidepressant Response in Clinical Care (EMBARC) study who had completed the CAST scale at baseline. The scale's five‐domain (irritability, anxiety, mania, insomnia, and panic) structure was evaluated with confirmatory factor analysis. Correlations with other clinical measures were used to confirm convergent and divergent validity. Logistic regression analyses from CO‐MED were used to estimate individual outcomes in EMBARC. RESULTS: Cronbach's alpha for the CAST scale was 0.78. Model fit for the five‐domain structure was adequate (goodness of fit index=0.93, comparative fit index=0.92, root mean square error of approximation=0.06). Scores on irritability, anxiety, panic, insomnia, and mania were correlated with scores on the Anger Attack Questionnaire irritability item (r(s)=0.50), Hamilton Rating Scale for Depression anxiety subscale (r(s)=0.24), Mood and Anxiety Symptoms Questionnaire anxious arousal scale (r(s)=0.44), Quick Inventory of Depressive Symptomatology Self‐Report insomnia items (r(s)=0.38), and Altman Self‐Rating Mania Scale (r(s)=0.39), respectively. Individual outcomes of remission (area under the curve [AUC]=0.805) and no meaningful benefit (AUC=0.779) were predicted with high accuracy among EMBARC participants using their baseline and week 4 scores for depression and irritability and model estimates from CO‐MED. CONCLUSIONS: Measuring irritability may help predict clinical course. The CAST scale is a valid measure of depression‐associated symptoms, including irritability.