Known-Groups Cross-Validation of the Letter Memory Test in a Compensation-Seeking Mixed Neurologic Sample

Abstract

Compensation-seeking neuropsychological evaluees were classified into Honest (HON; n = 37) or Probable Cognitive Feigning (PCF; n = 53) groups based on results from the Victoria Symptom Validity Test, the Test of Memory Malingering, and the Digit Span subtest of the Wechsler Adult Intelligence Scale--3rd ed. The groups were generally comparable on demographic, background, and injury severity characteristics, although HON TBI participants were significantly more likely to have a documented loss of consciousness, whereas PCF participants were significantly more likely to be currently on disability. PCF participants scored significantly lower on many neuropsychological test, particularly of memory, as well as higher on most MMPI-2 clinical scales. The PCF group also had significantly higher scores on multiple indices of feigning of psychiatric symptoms. Results from the Letter Memory Test (LMT) were significantly lower for the PCF group, and using the recommended cutting score, specificity was .984, whereas sensitivity was .640, suggesting adequate performance on cross-validation.

Feigned neurocognitive deficit: Taxon or dimension?

“…With a high level of success among genuine patients, the LMT uses a floor effect strategy. A cross-validational study also found support for the discriminative validity of the LMT using a cutoff score of <93% correct as evidence of malingering (Vagnini et al, 2006).…”

Evaluating the gold standard: A review and meta-analysis of the Structured Interview of Reported Symptoms.

“…Despite these significant group differences, variability within similar studies was still pronounced. For example, some clinical samples obtained very low mean total scores (e.g., neuropsychiatrically impaired patients obtained a mean total score of 18.5; Vagnini et al (2006), and one study of forensic psychiatric patients referred for evaluations of competency to stand trial observed a mean total score of 32.5; Gothard et al, 1995). Yet, other studies reported extremely high mean scores among clinical samples thought to be responding honestly.…”

“…Studies conducted since the publication of the SIRS have also included more varied samples than those included in the initial validation studies. Researchers, including Rogers himself, have evaluated the accuracy of the SIRS in identifying feigning among adolescents (Dearth, 2006; Rogers et al, 1996) and patients with mental retardation (Farkas, 2008; Hayes, Hale, & Gouvier, 1998; Hurley & Deal, 2006), cognitive impairment (Rogers et al, 2009; Vagnini et al, 2006), dissociative identity disorder (Brand, McNary, Loewenstein, Kolos, & Barr, 2006), and posttraumatic stress disorder (Eakin, 2004; Landis, 1996). In addition to diverse samples, a number of researchers have varied the length and structure of the SIRS, exploring verbally administered abbreviated versions (Green, Rosenfeld, Dole, Pivovarova, & Zapf, 2008; Story, 2000) and paper-and-pencil formats (Landis, 1996; Norris & May, 1998).…”

Use of the SIRS in compensation cases: An examination of its validity and generalizability.

“…It uses a cut score <93% for the classification of cognitive feigning and appears effective in head-injured populations (Vickery et al, 2004). Additionally, it has been found useful in both simulation and known-groups designs (Vagnini et al, 2006).…”