Discriminant validity of the Social Phobia and AnxietyInventory (SPAI), the Social Phobia Scale (SPS) and theSocial Interaction Anxiety Scale (SIAS)Lorna Petersa,b,*aClinical Research Unit for Anxiety Disorders, St Vincent's Hospital, 299 Forbes St, Darlinghurst, NSW 2010,Australia.bSchool of Psychiatry, University of New South Wales, Sydney, NSW, Australia.Received 28 June 1999AbstractThree measures commonly used in assessment of social phobia, the Social Phobia and AnxietyInventory (SPAI [Turner, S. M., Beidel, D. C. & Dancu, C. V. (1996). Social phobia and anxietyinventory: manual. Toronto, Ont.: Multi-Health Systems Inc.), the Social Phobia Scale (SPS [Mattick, R.P. & Clarke, J. C. (1998). Development and validation of measures of social phobia scrutiny fear andsocial interaction anxiety. Behaviour Research and Therapy, 36, 455±470] and the Social InteractionAnxiety Scale (SIAS [Mattick, R. P. & Clarke, J. C. (1998). Development and validation of measures ofsocial phobia scrutiny fear and social interaction anxiety. Behaviour Research and Therapy, 36, 455±470],were compared for their ability to discriminate between social phobia and other anxiety disorders (panicdisorder with or without agoraphobia). Participants were 117 patients attending a specialized anxietydisorders unit for treatment. While all three measures were able to detect dierences between socialphobic patients and patients with panic disorder with or without agoraphobia, a logistic regressionanalysis showed that the SPAI, but not the SPS and SIAS, was a signi®cant predictor of membership ofthe social phobia group. Receiver operating characteristic (ROC) analysis also showed that the SPAIwas the better measure for discriminating between social phobia and panic disorder with and withoutagoraphobia. Analysis of the sensitivity, speci®city and positive and negative predictive power of themeasures at the optimum cuto scores produced by the ROC analysis are presented. 7 2000 ElsevierScience Ltd. All rights reserved.Keywords: Measurement of social phobia; Discriminant validityBehaviour Research and Therapy 38 (2000) 943±9500005-7967/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved.PII: S 0005 - 79 67 (9 9) 00 13 1- Xwww.elsevier.com/locate/brat* Tel.: +61-2-9332-1013; fax: +61-2-9332-4316.E-mail address: [email protected] (L. Peters).There are a number of reliable and valid self-report measures that can be used to measureaspects of social phobia (see Cox & Swinson, 1995, for a review). The focus of the presentpaper is the discriminant validity of social phobia measures Ð in particular, the ability ofmeasures to discriminate social phobia from other anxiety disorders.One of the most widely used measures in studies of social phobia is the Fear of NegativeEvaluation (FNE) scale developed by Watson and Friend (1969) along with its companionmeasure the Social Avoidance and Distress (SAD) scale. Although the development of thesemeasures preceded the inclusion of social phobia in the diagnostic classi®cation scheme, theyare widely used in studies of social phobia perhaps because it seems that the features tapped bythe measures are at the core of the disorder. The evidence does not, however, suggest that theFNE and SAD discriminate between anxiety disorder groups. Turner, McCanna and Beidel(1987) found that scores on the SAD and FNE were not signi®cantly dierent for participantswith social phobia, agoraphobia with and without panic disorder, panic disorder, generalizedanxiety disorder and obsessive compulsive disorder. Only participants with simple phobia weresigni®cantly dierent on their FNE and SAD scores from social phobic participants. Oei,Kenna and Evans (1991) found a similar pattern of results with no signi®cant dierences onthe SAD and FNE between participants with social phobia, panic disorder with agoraphobiaand generalized anxiety disorder. While the SAD showed signi®cant dierences betweenparticipants with social phobia and those with panic disorder or simple phobia, the FNE onlyshowed signi®cant dierences between participants with social phobia and participants withsimple phobia.Three alternative measures which were designed to assess social phobia speci®cally are thepair of measures called the Social Phobia Scale (SPS) and the Social Interaction Anxiety Scale(SIAS; Mattick & Clarke, 1998) and the Social Phobia and Anxiety Inventory (SPAI; Turner,Beidel & Dancu, 1996; Turner, Beidel, Dancu & Stanley, 1989). The SPS was designed tomeasure social phobia de®ned as ``anxiety and fear at the prospect of being observed orwatched by other people, and in particular, where the individual expresses distress whenundertaking certain activities in the presence of others'' (Mattick & Clarke, 1998, p. 457). TheSIAS scale was designed to measure social interaction anxiety de®ned as ``distress whenmeeting and talking with other people'' (Mattick & Clarke, 1998, p. 457). Thus the twocompanion measures were designed to distinguish between scrutiny fears and concerns aboutinteraction. In the original study of the measures, Mattick and Clarke (1998) showed that bothscales were able to discriminate between social phobia, agoraphobia and simple phobia samplesand between social phobia and normal samples. Heimberg, Mueller, Holt, Hope and Liebowitz(1992) found that the scales discriminated between social phobic and community samples.Brown et al. (1997) found that the scales discriminated between social phobics and otheranxiety disorder groups and control participants, with the exception of agoraphobicparticipants who could not be discriminated from social phobic participants on the basis of theSPS.The SPAI was developed on an empirical basis to assess social phobia and in particular toassess ``speci®c somatic symptoms, cognitions and behavior across a range of potentially fear-producing situations'' (Turner et al., 1989, p. 35). The SPAI score (scored as the dierencebetween the social phobia subscale and the agoraphobia subscale) has been shown todiscriminate between socially anxious and nonsocially anxious participants (Beidel, Turner,L. Peters / Behaviour Research and Therapy 38 (2000) 943±950944Stanley & Dancu, 1989) and between participants with social phobia and those with panicdisorder with or without agoraphobia or those with obsessive±compulsive disorder (Turner etal., 1989).In a direct comparison of the SPS, the SIAS and the SPAI in patients with social
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