Prevalence of anxiety in patients with an implantable cardioverter defibrillator: measurement equivalence of the HADS-A and the STAI-S

PURPOSE: The Hospital Anxiety and Depression Scale (HADS-A) and State-Trait Anxiety Inventory (STAI-S) are popular instruments for assessing anxiety and are considered interchangeable, although little is known about their equivalence. Hence, we examined whether the two instruments are (i) equivalent with respect to determining the prevalence of probable clinical anxiety levels and (ii) reflect variation on a common anxiety attribute. METHODS: Score and construct concordance were evaluated using equipercentile equating and bifactor modeling, respectively. Secondary data from the WEBCARE trial and the MIDAS study were used for the current study, where patients implanted with a first-time implantable cardioverter defibrillator completed both the HADS-A and the STAI-S within 10 days post implant. RESULTS: Data from 710 patients were included in the analyses. Results showed that the STAI-S produced a higher prevalence rate than the HADS-A (39% vs. 23%). A crosswalk table was generated with equivalent scores and cutoffs for the HADS-A and STAI-S, respectively. Bifactoring suggested that HADS-A and STAI-S largely tapped into the same generic anxiety attributes. CONCLUSIONS: STAI-S and HADS-A reflect a common anxiety attribute, but using the recommended cutoff scores on the respective measures show very different prevalence rates and would classify patients as anxious with the STAI-S who would not be identified as such with the HADS-A. Clinicians and researchers should be aware of the inequivalence when using these measures for screening and determining the prevalence of probable clinical anxiety levels.