Classification accuracy of the Portland digit recognition test in persons claiming exposure to environmental and industrial toxins.

The classification accuracy of the Portland digit recognition test (PDRT) in detecting cognitive malingering was studied in patients claiming cognitive deficits due to exposure to environmental or industrial toxins. Twenty-nine patients alleging toxic exposure and who met Slick et al. [Slick, D. J., Sherman, E. M. S., & Iverson, G. L. (1999). Diagnostic criteria for malingering neurocognitive dysfunction: Proposed standards for clinical practice and research. The Clinical Neuropsychologist, 13, 545-561] criteria for malingered neurocognitive dysfunction were compared to 14 toxic exposure patients negative for evidence of malingering. The published cutoffs were associated with a false positive error rate of 0% and sensitivity of more than 50%. When criterion for a PDRT failure was a positive PDRT finding on more than one section, the FP rate remained 0% while sensitivity improved to about 70%. The results indicate that a failed PDRT is an indication of malingering and not the neurological effect of a toxic substance or some other clinical phenomenon. The PDRT can be used with confidence as an indicator of negative response bias in cases of alleged exposure to neurotoxic substances.

Malingering in toxic exposure: classification accuracy of reliable digit span and WAIS-III Digit Span scaled scores.

This study examined the sensitivity and false-positive error rate of reliable digit span (RDS) and the WAIS-III Digit Span (DS) scaled score in persons alleging toxic exposure and determined whether error rates differed from published rates in traumatic brain injury (TBI) and chronic pain (CP). Data were obtained from the files of 123 persons referred for neuropsychological evaluation related to alleged exposure to environmental and industrial substances. Malingering status was determined using the criteria of Slick, Sherman, and Iverson (1999). The sensitivity and specificity of RDS and DS in toxic exposure are consistent with those observed in TBI and CP. These findings support the use of these malingering indicators in cases of alleged toxic exposure and suggest that the classification accuracy data of indicators derived from studies of TBI patients may also be validly applied to cases of alleged toxic exposure.

The prevalence of cognitive malingering in persons reporting exposure to occupational and environmental substances.

OBJECTIVE: Directly estimate the prevalence of cognitive malingering in persons claiming exposure to occupational and environmental substances. METHODS: Retrospective review of 128 neuropsychological cases with financial incentive. Estimates were based on two methods: (1) clinical identification using the Slick, Sherman and Iverson criteria for malingered neurocognitive dysfunction (MND), and (2) statistical modeling based on patient performance on several individual psychometric indicators of malingering. RESULTS: The prevalence based on the clinical method was 40%. The statistically based estimates ranged from 30% to more than 45% depending on model parameters. Different incentive parameters may influence prevalence. CONCLUSIONS: Cognitive malingering in toxic exposure is common and must be adequately addressed in the clinical neuropsychological assessment of toxic exposure and in research on its neurocognitive effects or findings will likely over-estimate the degree of cognitive impairment and related disability.

Classification accuracy of the Test of Memory Malingering in persons reporting exposure to environmental and industrial toxins: Results of a known-groups analysis.

This study used a known-groups design to examine the classification accuracy of the Test of Memory Malingering in detecting cognitive malingering in patients claiming cognitive deficits due to exposure to environmental and industrial toxins. Thirty-three patients who met Slick et al. criteria for Malingered Neurocognitive Dysfunction were compared to 17 toxic exposure patients negative for evidence of malingering, 14 TBI patients and 22 memory disorder patients, both groups without incentive. The original cutoffs (<45) for Trial 2 and Retention demonstrated perfect specificity (0% false positive error rate) and impressive sensitivity (>50%). These findings indicate the TOMM can be used with confidence as an indicator of negative response bias in cases of cognitive deficits attributed to exposure to alleged neurotoxic substances.

Pain, malingering and the WAIS-III Working Memory Index.

BACKGROUND CONTEXT: Pain patients often report cognitive symptoms, and many will include them in their claims of disability. There is empirical evidence that patients with pain do experience problems on attention-demanding cognitive tasks, but the results are mixed and the potential impact of exaggeration in the context of pain-related litigation has not been addressed. PURPOSE: 1) Examine the impact of pain and malingering on attention; 2) determine if the Working Memory Index (WMI) of the Wechsler Adult Intelligence Scale-3 (WAIS-III) can reliably detect malingering. STUDY DESIGN/SETTING: Study 1: simulator design; Study 2: clinical known-groups design. PATIENT SAMPLE: Study 1 used healthy college students; Study 2 used chronic pain patients and neurological patients. OUTCOME MEASURES: The WMI and its constituent subtests. METHODS: Study 1: College students were administered the WMI under three conditions: standard administration, with cold-pressor induced pain, or with instructions to simulate impairment due to pain. Study 2: Known-groups design in which the WMI was examined in non-malingering and definite malingering chronic pain patients, non-malingering moderate-severe traumatic brain injury, and memory disorder patients seen for routine psychological evaluation. Malingering was operationalized using published criteria. RESULTS: There were no group differences in WMI or its subtests among non-malingering groups, but some individual clinical patients with pain did score at a level suggestive of attentional impairment. The lowest scores were found in the simulated malingering college students and definite malingering clinical pain groups, in which about half scored worse than 95% of the non-malingering clinical patients. CONCLUSIONS: This study demonstrated that even when controlling for exaggeration some pain patients do exhibit problems with attentional function. However, significant impairment in WMI performance (eg, index score

Test of Memory Malingering Performance is unaffected by laboratory-induced pain: implications for clinical use.

The Test of Memory Malingering (TOMM) is a well-validated and widely used forced-choice symptom validity test. However, little is known about how TOMM performance is affected by pain. The present study evaluated the sensitivity of the TOMM to pain induced in healthy participants via the cold-presser test. Participants (n=20 per group) were administered the TOMM under one of three conditions: (1) standard instructions; (2) instructions to simulate pain-related memory deficit in pursuit of personal injury litigation; (3) while experiencing cold-induced pain. Results indicate that TOMM performance was unaffected by laboratory-induced moderate to severe pain and support the TOMM's use in evaluating clinical patients with pain.

Reliable digit span is unaffected by laboratory-induced pain: implications for clinical use.

Reliable Digit Span (RDS) is an indicator used to assess the validity of cognitive test performance. Scores of 7 or lower suggest poor effort or negative response bias. The possibility that RDS scores are also affected by pain has not been addressed thus potentially threatening RDS specificity. The current study used cold pressor-induced pain to investigate the effect of pain on RDS scores. Sixty undergraduate volunteers randomly assigned to one of three conditions (control, simulator, pain) completed the Digit Span subtest from the Wechsler Adult Intelligence Scale-III from which the RDS is derived. No differences in RDS scores were found between the control and pain groups, and neither group scored below 8. Sixty-five percent of the simulator group scored 7 or below. These results suggest that RDS is not affected by pain, and scores of 7 or less in persons with pain can be more confidently attributed to negative response bias.