Structured Interview of Reported Symptoms (SIRS)

The Structured Interview of Reported Symptoms (SIRS) is a fully structured interview that is designed to assess feigned mental disorders and related response styles. Each of its eight primary scales was constructed to evaluate well-established detection strategies for differentiating between malingered and genuine psychopathology. These primary scales consist of Rare Symptoms (RS), Symptom Combinations (SC), Improbable and Absurd Symptoms (IA), Blatant Symptoms (BL), Subtle Symptoms (SU), Selectivity of Symptoms (SEL), Severity of Symptoms (SEV), and Reported Versus Observed Symptoms (RO).

Description and Development of the SIRS

The initial development of the SIRS was based on an exhaustive review of potential detection strategies for feigned mental disorders. SIRS scales were developed based on the likely effectiveness of the underlying detection strategy and the adaptability of each strategy to interview-based assessments. Final item selection was based on independent judgments by eight experts in malingering and was subsequently refined to improve scale homogeneity. The SIRS is composed of 173 items that are organized by eight primary and five supplementary scales.

The original validation of the SIRS combined samples from multiple studies to form four groups: 100 inpatients and outpatients, 97 controls from community, correctional, and college settings, 170 simulators including coached and uncoached participants, and 36 likely malingerers from forensic settings. Subsequent validation research has included clinical and correctional samples with an additional 255 participants.

Reliability of the SIRS

Internal consistencies (alpha coefficients) for SIRS primary scales were excellent: They ranged from .77 to .92, with a mean alpha of .86. The reliability of individual scores was examined via standard errors of measurement (SEM). The SEMs were low for both clinical and control samples, indicating high reliability for individual scores. A central issue for the SIRS was its interrater reliability. These estimates were impressive, ranging from .89 to 1.00. The median reliability was .99, which represents almost perfect agreement.

Validity of the SIRS

SIRS validation relied on a combination of simulation designs and known-group comparisons. The simulation design capitalizes on internal validity in its use of analog research with clinical comparison samples. In contrast, known-group comparisons provide unmatched external validity in their use of individuals from actual clinical-forensic settings who were independently evaluated as malingering by established experts. For the assessment of malingering, convergent results from simulation and known-group studies provided the strongest evidence of SIRS validity.

A major focal point of the SIRS is its discriminant validity. The critical issue is whether each of the primary scales systematically differentiates between genuine and feigned psychopathology. Combining across studies, effect sizes can be computed for the critical distinctions (a) simulators versus clinical honest and (b) suspected malingerers versus clinical honest. For simulators, Cohen’s d’s were very large: They ranged from 1.40 (SU) to 2.31 (RS) with an average d of 1.74. Cohen’s d’s were also very large for suspected malingerers but showed less variability: 1.20 (IA) to 1.98 (SEL). The average effect size for malingerers was identical to that of simulators (d = 1.74). These combined data provide very strong evidence of discriminant validity.

Convergent validity was evaluated by comparing the SIRS with other measures of feigned mental disorders. The SIRS evidenced robust correlations with MMPI-2 validity scales. For example, the SIRS primary scales are strongly correlated with Scale F (r’s from .71 to .80). As also expected, they are negatively correlated with Scale K (Mr = -.35), a measure of defensiveness.

Construct validity was examined via discriminant analysis and factor analysis. A two-stage, stepwise discriminant analysis with a canonical correlation of .79 demonstrated the usefulness of SIRS primary scales for the accurate differentiation of feigned from clinical honest profiles. A high level of accuracy was maintained across calibration and cross-validation samples. Recently, a confirmatory factor analysis yielded strong support for a two-factor model of the SIRS (i.e., spurious presentations and plausible presentations) that was theoretically relevant to the assessment of malingering.

Forensic Applications of the SIRS

The SIRS is widely accepted as one of the best-validated measures of feigned mental disorders in clinical and forensic settings. Its classification of malingering in forensic settings is highly accurate. These classifications are based on either (a) three or more primary scales in the probable feigning range or (b) one or more primary scales in the definite feigning range. The probable feigning range was established so that it would include most feigners (typically >75%) but very few genuine patients (<10%). By using the established criterion (>3 scales in the probable feigning range), very few genuine patients were misclassified as feigners (i.e., 2.1% at 3 scales; 0.0% at > 4 scales). Scales in the definite feigning range are set very high to minimize false positives.

Research by other investigators generally confirms the accuracy of the SIRS and its low false-positive rates. Ongoing research suggests that the SIRS provides useful data for civil-forensic applications such as disability evaluations. As a caution, the initial data indicate that its cut scores may not be useful for a subset of inpatients with dissociative disorders and multiple traumas beginning before adulthood.

Future Directions

Research is currently under way for validating a Spanish-language SIRS. The SIRS was independently translated by three bilingual psychologists. The composite translation was back-translated by an independent bilingual psychologist; minor discrepancies were found for only 11.0% of the SIRS items. A revised Spanish SIRS was subjected to further translations and reviews. With the Spanish SIRS established, the comparability of the Spanish and English SIRS is currently being tested with bilingual Hispanic patients.

References:

  1. Rogers, R. (Ed.). (1997). Clinical assessment of malingering and deception (2nd ed.). New York: Guilford Press.
  2. Rogers, R., Bagby, R. M., & Dickens, S. E. (1992). Structured Interview of Reported Symptoms (SIRS) and professional manual. Odessa, FL: Psychological Assessment Resources.
  3. Rogers, R., Jackson, R. L., Sewell, K. W., & Salekin, K. L. (2005). Detection strategies for malingering: A confirmatory factor analysis of the SIRS. Criminal Justice and Behavior, 32, 511-525.
  4. Rogers, R., & Shuman, D. (2005). Fundamentals of forensic practice: Mental health and criminal law. New York: Springer.

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