526 TREATMENT OF SPECIFIC ANXIETY DISORDERS
rater reliability, excellent diagnostic utility, strong convergent validity, and sensitivity
to clinical change when used by trained and calibrated interviewers, although less is
known about its discriminant validity. Clearly, the CAPS is the recommended diagnos-
tic interview protocol for PTSD. The CAPS is available from the National Center for
PTSD (www.ncptsd.va.gov/ncmain/assessment).
Impact of Event Scale
The Impact of Event Scale (IES) is a 15-item questionnaire developed by Horowitz, Wil-
ner, and Alvarez (1979) to assess intrusion and avoidance symptoms of trauma exposure.
After the publication of DSM-IV a revised 22-item version (IES-R) was developed that
includes six new items on hyperarousal and one item concerning dissociative reexperi-
encing symptoms or flashbacks (Weiss & Marmar, 1997). More psychometric research
is needed on the IES-R before it can be used in clinical practice (Keane et al., 2007).
Mississippi Scale for Combat- Related PTSD
The Mississippi Scale for Combat- Related PTSD (MPTSD) is a 35-item questionnaire
designed to assess combat- related PTSD symptoms (Keane, Caddell, & Taylor, 1988)
that has been updated to reflect DSM-IV criteria. Respondents rate the severity of symp-
toms on a Likert scale in the time interval after experiencing trauma. The MPTSD has
excellent psychometric properties including high internal consistency (a = .94), one week
test- retest reliability (r = .97), diagnostic utility and convergent validity (Keane et al.,
1988; McFall, Smith, Roszell, Tarver, & Malas, 1990). A cutoff score of 106 or above
may be optimal for determining a diagnosis of PTSD (Keane et al., 2007). The MPTSD
is recommended when assessing combat- related PTSD.
Posttraumatic Stress Diagnostic Scale
The Posttraumatic Stress Diagnostic Scale (PDS) is a self- report questionnaire that pro-
vides a diagnosis of DSM-IV PTSD and assesses symptom severity (Foa, Cashman,
Jaycox, & Perry, 1997). It has a checklist of 12 traumatic events from which respon-
dents select the one that disturbed them most in the past month. Individuals then use
a four-point rating scale to indicate the frequency over the past month of the 17 core
symptoms of DSM-IV PTSD. An additional nine items assess impairment in different
areas of daily function. A score of 1 or higher is required on symptoms in order to count
toward a diagnosis of PTSD and the 17 symptom items can be summed to produce a
severity score. In the validation study PDS Total Symptom Severity differentiated those
who met a SCID diagnosis of PTSD from a non-PTSD group, had high internal con-
sistency (alpha = .92), good 2 week test– retest reliability (r = .83), and high agreement
(82%) with a SCID diagnosis. PDS Total Symptom Severity also correlates highly with
CAPS Total (r = .71) and the recommended cutoff score of 15 shows high sensitivity (i.e.,
89% of PTSD correctly identified) but poor specificity (Griffin, Uhlmansiek, Resick, &
Mechanic, 2004). Griffin and colleagues concluded that the PDS is a good proxy to a
full CAPS interview but tends to overestimate the prevalence of PTSD. The PDS is avail-
able from National Computer Systems (1-800-627-7271).