Medication use and the assessment of agoraphobic avoidance

Psychometric properties of the mobility inventory for agoraphobia: convergent, discriminant, and criterion-related validity

Aims of this study were (a) to summarize the psychometric literature on the Mobility Inventory for Agoraphobia (MIA), (b) to examine the convergent and discriminant validity of the MIA's Avoidance Alone and Avoidance Accompanied rating scales relative to clinical severity ratings of anxiety disorders from the Anxiety Disorders Interview Schedule (ADIS), and (c) to establish a cutoff score indicative of interviewers' diagnosis of agoraphobia for the Avoidance Alone scale. A meta-analytic synthesis of 10 published studies yielded positive evidence for internal consistency and convergent and discriminant validity of the scales. Participants in the present study were 129 people with a diagnosis of panic disorder. Internal consistency was excellent for this sample, α=.95 for AAC and .96 for AAL. When the MIA scales were correlated with interviewer ratings, evidence for convergent and discriminant validity for AAL was strong (convergent r with agoraphobia severity ratings=.63 vs. discriminant rs of .10-.29 for other anxiety disorders) and more modest but still positive for AAC (.54 vs. .01-.37). Receiver operating curve analysis indicated that the optimal operating point for AAL as an indicator of ADIS agoraphobia diagnosis was 1.61, which yielded sensitivity of .87 and specificity of .73.

Dimensions of agoraphobia assessed by the Mobility Inventory

Factor analyses of the When Accompanied and When Alone subscales of the Mobility Inventory (Chambless, Caputo, Jasin, Gracely & Williams, Behaviour Research and Therapy, 23, 35-44, 1985) were conducted using the responses of 177 panic disorder with agoraphobia patients. For both subscales a three-factor model was the most appropriate and accounted for approx. 60% of the variance in each case. The three factors were reliable and theoretically meaningful: fear of public places, enclosed spaces and open spaces. The fear of public places factor accounted for most of the explained variance and is discussed in relation to the social evaluation component of panic attacks.