Development of an abbreviated Social Phobia and Anxiety Inventory (SPAI) using item response theory: The SPAI-23

An abbreviated version of the Social Phobia and Anxiety Inventory (SPAI) was developed using methods based in nonparametric item response theory. Participants included a nonclinical sample of 1,482 undergraduates (52% female, mean age = 19.4 years) as well as a clinical sample of 105 individuals (56% female, mean age = 36.4 years) diagnosed with either generalized (73%) or specific social phobia (27%). Twenty-three of the 45 SPAI items demonstrated good discrimination along the social anxiety continuum. In addition, option characteristic curves (OCCs) indicated that the SPAI's 7-point scale may generate errors in ranking individuals. Thus, options were collapsed to improve item performance. No gender differences emerged between any of the items' OCCs, suggesting that items function similarly among men and women. The abbreviated version also correlated highly with the original 45-item SPAI and exhibited similar patterns of correlations with measures of social anxiety. The SPAI-23 has considerable practical benefits, including a screening of both social and agoraphobic anxiety as well as decreased assessment and scoring time.