Derivation of the SPAN, a brief diagnostic screening test for post-traumatic stress disorder
Introduction
Post-traumatic stress disorder (PTSD) is a major mental health issue having a lifetime prevalence in the US of between 8 and 12%. It frequently becomes a chronic problem, and there are substantial rates of psychiatric and medical comorbidity found in association with PTSD (Kessler et al., 1995). Since PTSD was first introduced into the DSM-III (American Psychiatric Association, 1980), the need for accurate diagnosis of PTSD has led to the development of instruments for measuring the disorder.
The structured clinical interview has been regarded as the gold standard of PTSD measurement (Gerardi et al., 1989). These interviews include the Structured Clinical Interview for DSM-III-R (Spitzer et al., 1990), the Structured Interview PTSD measure (SIP) (Davidson et al., 1997a), and the Clinician Administered PTSD Scale (CAPS) (Blake et al., 1995). All have demonstrated good psychometric validity and reliability criteria and have been used extensively in treatment outcome studies.
However, a major drawback of structured clinical interviews is that they are time consuming, and thus, briefer self-rating scales may be viewed as having potential clinical utility. A number of self-rating scales have been developed to assess the symptoms of PTSD while economizing on time. These include the Impact of Events Scale (IES) (Horowitz et al., 1979), the Mississippi Scales for Combat and Non-combat (Keane et al., 1988), the Short Form of the Mississippi Scale (Fontana and Rosenheck, 1994), the Penn Inventory (Hammarberg, 1992), the PTSD Checklist (PCL) (Weathers et al., 1993), the Post-traumatic Stress Diagnostic Scale (PDS) (Foa, 1995), and the Davidson Trauma Scale (DTS) (Davidson et al., 1997b).
Given the abundance of instruments and a rapidly expanding empirical literature, researchers and clinicians can now choose instruments tailored to their particular assessment needs. In addition, they can increase their confidence in assessment decisions by relying on converging information obtained from multiple measures in an assessment battery (Keane et al., 1987). In particular, the use of a structured clinical interview as well as self-rating scales has become widely accepted as a way of obtaining diagnosis and/or assessing severity and clinical significance of symptoms.
The Davidson Trauma Scale (DTS) is a validated 17-item self-rating scale of frequency and severity of each symptom, which is sensitive to the effects of treatment (Davidson et al., 1997b). The DTS reflects the symptoms diagnostic of PTSD as defined in DSM-IV (American Psychiatric Association, 1994). Major strengths of the DTS include its development in a broad population of men and women exposed to different types of trauma, its sensitivity to treatment-induced change across time, and its capability of distinguishing between treatments of differing effectiveness and its ability to predict later treatment response. The full DTS has been shown to distinguish between those with, and those without, a diagnosis of PTSD at a cutoff score of 40, with an efficiency of 0.83.
Since the 17 items of the DTS demonstrate a high level of intercorrelation with one another (Cronbach’s alpha coefficient =0.90), we believed that it might be possible to develop a much shorter version of the scale to serve as a diagnostic screening tool. The newly derived four-item scale (SPAN) forms the subject of this report.
Section snippets
Subjects
Item selection for the SPAN was drawn from a sample of 243 patients obtained from multiple cohorts which comprised both pharmacotherapy trials of lamotrigine (n=14) (Hertzberg et al., unpublished); fluvoxamine (n=12) (Davidson et al., 1998a); nefazodone (n=12) (Davidson et al., 1998b); and fluoxetine vs. placebo (n=55) (Connor et al., 1999); a family study of rape trauma (n=74) (Davidson et al., 1998c); an evaluation of Hurricane Andrew survivors (n=53) (Davidson et al., 1997b); and a group of
Results
A total of 243 patients were included in the analysis. The average age was 37 years (S.D.=11.6). Of the total group, 72% were women, 28% were men, 77.6% were Caucasian and 17.4% were African–American, and 5% were of other ethnic groups. All subjects were evaluated for a diagnosis of PTSD. Of the subjects 118 (48.6%) had a diagnosis of PTSD, while 125 subjects (51.4%) had no diagnosis of PTSD. The demographic data were calculated for both derivation and replication groups as shown in Table 1.
Discussion
We found that a short four-item version of the DTS closely corresponded to the diagnosis of PTSD by structured clinical interview and believe, therefore, that it could be effectively used to screen for the diagnosis. We refer to this scale as the SPAN, a readily usable acronym, which conveys its content in the following way: Startle, Physiological arousal, Anger and Numbness. Based upon SPAN scores, appropriate subjects could then receive a more in depth clinical evaluation. The four-item
Acknowledgements
Thanks are due to Drs Thomas Mellman, Jean Beckham, Michael Hertzberg, and Larry Tupler. This study was supported, in part, by grants from the National Institute of Mental Health (1RO1-MH44740 and RO1-MH47488) to Dr Davidson.
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