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

• Published in: Archives of clinical neuropsychology 2008-05, Vol.23 (3), p.341-350
• Main Authors: Greve, Kevin W., Bianchini, Kevin J., Heinly, Matthew T., Love, Jeffrey M., Swift, Douglas A., Ciota, Megan
• Format: Article
• Language: English
• Subjects: Adult; Adult and adolescent clinical studies; Biological and medical sciences; Cognition; Environment. Living conditions; Female; Humans; Known-groups design; Male; Malingering; Malingering - classification; Malingering - diagnosis; Malingering - etiology; Medical sciences; Middle Aged; Neuropsychological assessment; Neuropsychological Tests - statistics & numerical data; Neurotoxic exposure; Occupational Diseases - chemically induced; Occupational Diseases - diagnosis; Occupational Exposure - adverse effects; Organic mental disorders. Neuropsychology; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Public health. Hygiene; Public health. Hygiene-occupational medicine; Recognition (Psychology) - physiology; ROC Curve; Sensitivity and Specificity; Symptom validity test
• ISSN: 0887-6177; 1873-5843
• DOI: 10.1016/j.acn.2007.12.001

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.