Clinician-Administered PTSD Scale (CAPS)

Summary	The CAPS is widely considered to be the "gold standard" in PTSD assessment. It is a structured interview providing a categorical diagnosis, as well as a measure of the severity of PTSD symptoms as defined by DSM-IV. It can be administered by any trained person and takes 30-60 minutes.
Author/publisher details	National Center for PTSD, Boston, USA. http://www.ncptsd.va.gov
Date	Although first published in 1990, it is usually referenced as 1995
Description	The CAPS is a structured interview designed to make a categorical PTSD diagnosis, as well as to provide a measure of PTSD symptom severity. The structure corresponds to the DSM-IV criteria, with B, C, and D symptoms rated for both frequency and intensity; these two scores are summed to provide severity ratings. Additional questions assess Criteria A, E, and F. The CAPS-IV also inquires about associated features of guilt and dissociation; the latter allow the interview to be used for assessment of Acute Stress Disorder (e.g., Creamer et al., 2004; O'Donnell et al., 2004), although nothing has been published to date on the validity of this approach. It takes 30-60 minutes to administer, (depending on the level of psychopathology) and slightly less to score. Training is required to administer this test, although all the necessary information for self-learning is available for free. Although ideal for research settings, it can be a little cumbersome for use in routine clinical practice especially for those less experienced with the interview.
Scoring and Psychometrics	Scoring It is recommended that the "1 - 2" rule be used to determine a diagnosis; that is, a frequency score of 1 (scale 0 = "none of the time" to 4 = "most or all of the time") and an intensity score of 2 (scale 0 = "none" to 4 = "extreme") is required for a particular symptom to meet criterion (Weathers et al., 1999). The diagnosis is then made according to the DSM-IV algorithm (i.e., 1 "B" Criteria, 3 "C" Criteria, and 2 "D" Criteria, along with A, E, and F). A severity score for each symptom is calculated by summing the frequency and intensity scores, which can then be summed for all 17 symptom questions and/or for the three symptom clusters. Alternative scoring options were suggested by Weathers et al., 1999, but they concluded that more complex systems were not well suited to routine clinical use. They note, however, that those options may be useful for differential diagnosis where a balance between false positives and false negatives is required. Psychometrics The CAPS has good psychometric properties across a wide variety of clinical populations and research settings (Weathers et al 2001). Inter-rater reliability is high, ranging from 0.92 to 1.00 for "Frequency" ratings and 0.93 to 0.98 for "Intensity" ratings; the global severity correlation was 0.89. (Hovens et.al., 1994). Kappa for a categorical PTSD diagnosis is often 1.0 (i.e., 100% agreement; e.g., Mueser et.al., 2001). Test-retest reliabilities range from .77-.96 for the three symptom clusters and from .90-.98 for the 17-item core symptom scale (Blake et.al., 1995). Using the standard 1/2 scoring rule described above, test-retest reliability (kappa) for a CAPS PTSD diagnosis was .63, with 83% agreement. The CAPS demonstrates high internal consistency, with alphas for the three symptom clusters ranging from .85-.87, and .94 for the total score (Blake et.al., 1995). Strong convergent validity has been demonstrated against the Structured Clinical Interview for DSM-IV (SCID) PTSD module (.83) and the PSS-I (.73) (Foa & Tolin, 2000). Overall agreement between a clinician-rated diagnosis and CAPS diagnosis was 79%; sensitivity was .74, while specificity was .84 (Hovens et.al., 1994). Several studies have reported strong agreement between the CAPS and various PTSD self report scales.
Key/core References	Blake, D. D., Weathers, F. W., Nagy, L. M., Kaloupek, D. G., Gusman, F. D., Charney, D. S., & Keane, T. M. (1995). The development of a clinician-administered PTSD scale. Journal of Traumatic Stress, 8, 75-90. Blake, DD, Weathers ,FW, Nagy LM, Kaloupek D, Klauminzer G, Charney DS, Keane TM, & Buckley TC. (2000). Clinician-Administered PTSD Scale (CAPS) Instruction Manual. Boston, MA: National Center for PTSD. Creamer, M., O'Donnell, M., & Pattison, P. (2004). The relationship between acute stress disorder and posttraumatic stress disorder in severely injured trauma survivors. Behaviour Research and Therapy, 42, 315-328. Foa, E. B., & Tolin, D. F. (2000). Comparison of the PTSD Symptom Scale-Interview Version and the Clinician-Administered PTSD scale. Journal of Traumatic Stress, 13, 181-191. Hovens, J. E., Van Der Ploeg, H. M., Klaarenbeek, M. T. A., Bramsen, I., Schreuder, J. N., & Rivero, V. V. (1994). The Assessment of Posttraumatic Stress Disorder: with the Clinician Administered PTSD Scale: Dutch Results. Journal of Clinical Psychology, 50, 325-340. Mueser, K. T., Rosenberg, S. D., Fox, L., Salyers, M. P., Ford, J. D., & Carty, P. (2001). Psychometric evaluation of trauma and posttraumatic stress disorder assessments in persons with severe mental illness. Psychological Assessment, 13, 110-117. O'Donnell, M., Creamer, M., Pattison, P., & Atkin, C. (2004). Psychiatric morbidity following injury.American Journal of Psychiatry, 161, 507-514. Weathers, F. W., Keane, T. M., & Davidson, J. (2001). Clinician-administered PTSD scale: A review of the first ten years of research. Depression and Anxiety, 13, 132-156. Weathers, F. W., Ruscio, A. M., & Keane, T. M. (1999). Psychometric properties of nine scoring rules for the Clinician-Administered Posttraumatic Stress Disorder Scale. Psychological Assessment, 11, 124-133.
Further Information (e.g., Links)	Training for administering the CAPS is available through the instruction manual, and also on a downloadable CD-ROM, although since the download is large and time consuming it is also available for purchase. See: http://www.ncptsd.va.gov/nomain/assessment/caps_request.html
View manual	A comprehensive administration manual is available ISTSS Members: Download CAPS Manual.
View tool	This resource should be used in an ethical and responsible manner and should be used only for the purpose(s) for which it has demonstrable validity. Please observe copyright where indicated and reference it appropriately. ISTSS Members: Download CAPS Interview Schedule.

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