Both the 17-item Hamilton Rating Scale for Depression (HRSD(17)) and 30-item Inventory of Depressive Symptomatology - Clinician-rated (IDS-C(30) ) contain a subscale that assesses anxious symptoms. We used classical test theory and item response theory methods to assess and compare the psychometric properties of the two anxiety subscales (HRSD(ANX) and IDS-C(ANX)) in a large sample (N = 3453) of outpatients with non-psychotic major depressive disorder in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Approximately 48% of evaluable participants had at least one concurrent anxiety disorder by the self-report Psychiatric Diagnostic Screening Questionnaire (PDSQ). The HRSD(ANX) and IDS-C(ANX) were highly correlated (r = 0.75) and both had moderate internal consistency given their limited number of items (HRSD(ANX) Cronbach's alpha = 0.48; IDS-C(ANX) Cronbach's alpha = 0.58). The optimal threshold for ascribing the presence/absence of anxious features was found at a total score of eight or nine for the HRSD(ANX) and seven or eight for the IDS-C(ANX) . It would seem beneficial to delete item 17 (loss of insight) from the HRSD(ANX) as it negatively correlated with the scale's total score. Both the HRSD(ANX) and IDS-C(ANX) subscales have acceptable psychometric properties and can be used to identify anxious features for clinical or research purposes.
Trial registration: ClinicalTrials.gov NCT00021528.
Copyright © 2011 John Wiley & Sons, Ltd.