Assessment and Diagnosis of Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a chronic and debilitating mental condition that develops in response to catastrophic life events, such as military combat, sexual assault, and natural disasters. The symptoms of PTSD are divided into 3 symptom clusters: reexperiencing, avoidance, and hyperarousal. In addition, trauma survivors often experience guilt, dissociation, alterations in personality, difficulty with affect regulation, and marked impairment in ability for intimacy and attachment.^1,2 Disorders comorbid with PTSD include depression, substance abuse, other anxiety disorders, and a range of physical complaints.^3,4

Over the past several decades, considerable progress has been made in the development and empirical evaluation of assessment instruments for measuring trauma exposure and PTSD as well as related syndromes, such as acute stress disorder. The measures that have been developed, including questionnaires, structured interviews, and psychophysiological procedures, have been extensively validated and many have been widely adopted internationally. PTSD assessments were developed to be psychometrically sound; to collect information from multiple sources across response channels; and to use across different trauma populations, settings, genders, ethnic groups, and cultures.^5-8

This article, based on a comprehensive review by Weathers and associates,⁹ provides a selective and brief summary of trauma and PTSD assessments in adults.

Diagnosing PTSD

The current diagnostic criteria for PTSD include¹⁰:

• Exposure to a traumatic stressor (criterion A)

• The development of a characteristic syndrome involving reexperiencing, avoidance and numbing, and hyperarousal symptoms (criteria B through D)

• Duration of at least 1 month (criterion E)

• Clinically significant distress or impairment in social or occupational functioning (criterion F).

A comprehensive assessment of PTSD evaluates all of the diagnostic criteria, assesses associated features and comorbid disorders, and establishes a differential diagnosis. Although some of these tasks can be accomplished with self-report measures, most are best accomplished with a structured interview. Clinical interviews provide opportunities to ask follow-up questions, to clarify items and responses, and to use clinical judgment in making the final ratings.

It is necessary to establish that an individual has been exposed to an extreme stressor that satisfies the DSM-IV definition of trauma as described in criterion A. The patient must have directly experienced the event, witnessed it, or learned about it indirectly; the event must have been life-threatening, involved serious injury, or threatened physical integrity; and it must have triggered an intense emotional response of fear, horror, or helplessness.

In addition to identifying an index event for symptom inquiry, it is important to assess for exposure to other traumatic events across the life span. Exposure to multiple lifetime traumas is typical, and previous traumas may influence reactions to the index event.^3,11 The target trauma is identified as the one that is currently causing the most frequent and severe symptoms. The 17 PTSD symptoms are then rated in relation to that event (Table 1). In addition to evaluating the diagnosis and severity of PTSD, a comprehensive assessment often includes an evaluation for the presence of comorbid disorders and associated features.

Several measures are available to help diagnose PTSD and assess its severity. These include structured interviews, self-report measures, and multiscale personality inventories (Table 2).

CHECKPOINTS
? Posttraumatic stress disorder (PTSD) assessment instruments are psychometrically sound, can be used to collect information from multiple sources, and can be used to measure different trauma populations.

? Although structured interviews, self-report measures, and multiscale personality inventories are available for assessing PTSD, a structured interview is recommended to evaluate all of the diagnostic criteria, assess associated features and comorbid disorders, and establish a differential diagnosis.

? In addition to identifying an index event for symptom inquiry, it is important to assess patients for exposure to other traumatic events across their life span.

Structured interviews

The comprehensive Structured Clinical Interview for DSM-IV (SCID) is designed to help diagnose all the major DSM-IV disorders.¹² As with all SCID modules, the PTSD module maps directly onto DSM-IV diagnostic criteria. The SCID PTSD module appears to have good reliability and convergent validity in a variety of samples and settings.^13-15

The Clinician-Administered PTSD Scale (CAPS), which was developed in 1989 at the National Center for PTSD, is a comprehensive structured interview for PTSD.^16,17 The CAPS consists of 30 items: 17 items assess DSM-IV symptoms of PTSD; 5 assess onset, duration, subjective distress, and functional impairment; 3 assess overall response validity, symptom severity, and symptom improvement; and 5 assess associated symptoms, including trauma-related guilt and dissociation. In addition, the CAPS assesses criterion A by means of the Life Events Checklist, which screens for possible trauma exposure. It also includes a trauma inquiry section that evaluates criterion A and identifies an index event for symptom inquiry. At the symptom level, the CAPS yields continuous and dichotomous scores for each item, and at the syndrome level it yields a continuous measure of overall PTSD symptom severity in addition to a dichotomous PTSD diagnosis.

The CAPS has been studied extensively and has excellent psychometric properties. It is the most widely used structured interview for PTSD and has proved useful for a variety of clinical and research assessment needs. The CAPS published version includes the interview booklet, an interviewer’s guide, and a technical manual. The main disadvantage of the CAPS is that it contains many more questions and therefore takes longer than other interviews to administer; it also requires additional training to become proficient in its administration and scoring. Finally, it yields 2 scores that need to be combined to yield an overall index of the intensity of the PTSD symptoms.

The PTSD Symptom Scale–Interview (PSS-I) is a structured interview developed by Foa and colleagues¹⁸ to assess DSM-III-R criteria for PTSD. It consists of 17 questions that correspond to the symptom criteria for PTSD. The current version, modified for DSM-IV, includes combined frequency and intensity ratings. The PSS-I yields a severity/frequency score for each of the 3 PTSD symptom clusters as well as a total PTSD severity score. It also yields a PTSD diagnosis, which is obtained by following a rationally derived scoring system whereby an item is counted as a symptom toward a diagnosis if it is rated as 1 or more.

The PSS-I has excellent psychometric properties.¹⁸ It has strong internal consistency, good test-retest re-liability, and excellent validity. Furthermore, it correlates strongly with several self-report measures of PTSD, depression, and anxiety.

In a recent report, the PSS-I generally compared favorably with the CAPS.¹⁹ The PSS-I took significantly less time to administer than did the CAPS. PSS-I is relatively brief and easy to administer; it yields a PTSD diagnosis as well as continuous severity scores for the 3 symptom clusters and the full syndrome. It includes only a single question for each symptom and offers instructions on how to follow up on ambiguous responses.

The Structured Interview for PTSD, developed to assess DSM-III and DSM-III-R criteria for PTSD, was modified in 1997 to correspond to DSM-IV criteria and relabeled as the SIP.^20,21 The SIP consists of 19 items, including 17 items that correspond to DSM-IV diagnostic criteria for PTSD and 2 items that measure trauma-related guilt. Items are rated on a 5-point scale and those that are rated as moderate or higher are considered symptom endorsements. The SIP yields a continuous measure of PTSD symptom severity as well as a dichotomous DSM-IV PTSD diagnosis.

The SIP has excellent interrater reliability and diagnostic agreement.²⁰ Good diagnostic utility against the SCID PTSD module was reported as well. For the revised version, in addition to excellent test-retest reliability and interrater reliability, moderate to strong correlations with self-report measures of PTSD have been reported, as had moderate correlations with measures of depression and anxiety.²¹ Furthermore, the SIP has shown good sensitivity to clinical change as a treatment outcome measure.

Self-report measures

The Posttraumatic Stress Diagnostic Scale (PDS) is a 49-item self-report measure designed to assess all the DSM-IV diagnostic criteria for PTSD.^22,23 The PDS, which is based on the self-report counterpart of the PSS-I (PSS-SR) is the only stand-alone instrument that assesses all DSM-IV criteria.¹⁸ It was designed as a screening instrument to identify PTSD in the general population or in a population of trauma survivors. The PDS is psychometrically sound.²³

There is strong internal consistency and good test-retest reliability across the 17 symptom items of the PDS.²² The PDS correlates well with self-report measures of PTSD, depression, and anxiety. The PDS total severity score and the total number of symptoms endorsed significantly discriminate persons with and without a PTSD diagnosis based on the SCID PTSD module. The PDS has adequate diagnostic utility against the SCID.

The PDS was developed with careful attention to content validity. It yields both a continuous measure of symptom severity and a PTSD diagnosis, and it has excellent psychometric properties. The PDS has been translated into numerous languages and its psychometric properties, which were examined in several cultures, replicate those found in the original study.

The PTSD Checklist (PCL) is a 17-item self-report measure of PTSD developed at the National Center for PTSD in 1990.²⁴ The 17 PCL items correspond to the 17 DSM-IV symptoms of PTSD. Respondents rate how much they have been bothered by each symptom during the past month using a 5-point scale. The PCL yields a continuous measure of PTSD symptom severity for each of the 3 symptom clusters and for the whole syndrome.

The PCL has been widely adopted (especially by Veterans Administration systems) and extensively evaluated, and it has excellent psychometric properties across a variety of trauma populations.^24-26 The PCL also correlates strongly with other measures of PTSD and combat exposure, and it has demonstrated good diagnostic utility against the SCID PTSD module.

The Davidson Trauma Scale (DTS) is another 17-item self-report measure that assesses DSM-IV diagnostic criteria for PTSD.²⁷ The format is similar to that of the CAPS in that the frequency and severity of each symptom is rated on separate 4-point scales. The time frame for ratings is the past week. This allows for frequent administrations, which is valuable in treatment outcome studies but limits the use of the DTS as a diagnostic measure.

The DTS appears to have good psychometric properties.²⁷ It has high internal consistency and strong test-retest reliability. It also demonstrates good convergent and discriminant validity and correlates strongly with several other PTSD measures. In addition, the DTS distinguishes between PTSD severity, and it is sensitive to changes in PTSD severity as a function of treatment. Finally, the DTS demonstrates good diagnostic utility against the SCID PTSD module.

The DTS appears to be a useful measure of PTSD. It is well suited for tracking changes in symptom severity in treatment outcome studies and has been widely adopted for this purpose.²⁸ One limitation is that little additional psychometric work has been conducted, so it is not clear how well the original findings can be generalized to other samples and settings.

Developed before the formal recognition of PTSD as a mental disorder in DSM-III, the Impact of Event Scale (IES) is the oldest standardized measure of posttraumatic symptoms.²⁹ Weiss and Marmar³⁰ developed a 22-item revised version (IES-R) by adding 6 hyperarousal items and 1 dissociative item and by changing the response dimension from symptom frequency to degree of subjective distress, expanding the number of response options from 4 to 5 and relabeling the anchors. The IES-R demonstrates the same high level of reliability and validity as the original IES.³¹ Both versions can be used effectively to assess trauma-related symptoms.

The Mississippi Scale for Combat-Related PTSD (Mississippi Scale) is a 35-item self-report measure of PTSD symptoms and associated features.³² Items are rated on a 5-point scale with anchors that vary according to item content. The Mississippi Scale is the most widely used measure of combat-related PTSD. It has excellent psychometric properties and was selected as the primary PTSD measure in the National Vietnam Veterans Readjustment Study (NVVRS).^6,32-35

Multiscale personality inventories

The Minnesota Multiphasic Personality Inventory (MMPI) is one of the oldest and most widely used psychological assessment instruments.³⁶ The MMPI was revised in 1989, and the MMPI-2, which incorporates a number of new features, has continued the tradition of the MMPI as a preeminent multiscale personality inventory.³⁷ The MMPI-2 permits a broad, psychometrically sound assessment of personality, psychopathology, and various forms of response bias.

The MMPI-2 assesses the wide range of problems typically seen in the clinical presentation of PTSD and provides sophisticated methods for detecting malingering and other types of response bias. Penk and associates³⁸ provide a thorough overview of the various clinical applications of the MMPI-2 and describe in some detail how information from the MMPI-2 can be integrated effectively with information from other sources.

Developed in 1991, the Personality Assessment Inventory (PAI) has grown rapidly in popularity in clinical, research, and forensic settings.³⁹ Because the PAI is a relatively new instrument, only a limited number of studies have investigated its use in the assessment of PTSD. However, the studies that have emerged indicate that the PAI has considerable promise and could be very useful as a research and clinical tool with trauma survivors.

Based on the relatively small amount of literature thus far, the PAI appears to have considerable merit for the assessment of PTSD. As with the MMPI-2, the PAI rigorously evaluates various forms of response bias, assesses a wide range of comorbid syndromes, and contains a specialized PTSD scale. Because it was developed in a construct validation approach, the PAI provides a straightforward assessment of contemporary constructs related to diagnosis and clinical management. In addition, preliminary evidence suggests that it has discriminant validity for distinguishing PTSD from other commonly comorbid disorders, such as depression.

SUMMARY

Considerable progress has been made in the development and evaluation of standardized measures for assessing trauma exposure and PTSD. A wide variety of instruments and protocols that can provide psychometrically sound and practicable measurement of PTSD for almost any application across settings is available. The use of such instruments is de rigueur for empirical studies and is increasingly expected in clinical settings as well. The growing focus on the use of evidence-based assessment procedures will foster the continued dissemination of such measures until they become part of routine clinical practice.

It is clear that scientific knowledge regarding the phenomenology, etiology, and treatment of PTSD will continue to broaden and deepen, and that sound measurement will play a vital role. The construct of PTSD has fostered a sustained and systematic investigation of the human response to trauma, and evidence-based assessment will continue to provide the foundation for the study and care of those persons who suffer the psychological toll of catastrophe.

References:

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