Effect Sizes of Impairment Associated with Symptom Exaggeration vs Effect Sizes of Impairment Associated with Symptom Exaggeration vs. Definite Traumatic Brain Injury Martin L. Rohling, Ph.D. Memorial Hospital at Gulfport, MS Paul Green, Ph.D. Neurobehavioral Associates, Edmonton, Alberta Lyle Allen, M.A. CogniSyst Inc., Durham, NC Paul Lees-Haley Paul Lees-Haley Corporation, Woodland Hills, CA

Introduction Valid neuropsychological assessment presupposes that the patient is putting forth the best possible effort on testing. In recent years it has become increasingly apparent that forensic assessment data are subject to a number of important response biases or invalid response sets, a significant one of which is suboptimal effort (Iverson and Binder, 2000). Most examiners control for a variety of characteristics of the patient. For example, age, education, gender, and intelligence partially explain scores on some tests and examiners correct for these factors. Until recently, the person’s effort on testing was not measured. Unquestionably effort is one of those characteristics of the examinee that predict performance on neuropsychological tests.

Historically, effort has been assessed by clinical judgment Historically, effort has been assessed by clinical judgment. Many have assumed that the degree to which fluctuating effort or consistently suboptimal effort has affected ability test scores or symptom reporting in a particular person is insignificant. Ideally, clinicians would not only be able to measure a person’s effort on testing, but they would also have a data-based guide to the likely influence of various degrees of effort on specific neuropsychological tests. Secondly, we need to know how varying degrees of effort affect particular cognitive domains, specific test instruments, and self rating scales. This requires the study of the results of many instruments and self rating scales, in large numbers of clinical cases, in whom effort has been simultaneously measured, using several methods.

Purpose The first purpose of the current study was to measure the extent to which effort affects the statistical variance in neuropsychological tests and also in symptom reporting scales in a large clinical sample of people undergoing neuropsychological assessment for purposes of evaluating eligibility for financial compensation. A second purpose was to identify the best predictor of test performance among several possible predictors, including measures of effort and also other variables, such as intelligence, age and diagnosis. The analysis included a ranking of several effort measures for predictive power. Finally, a third purpose was to rank several clinical measures in terms of their apparent sensitivity or vulnerability to suboptimal effort.

Methods Five measures of symptom validity were administered to a sample of 904 patients who were referred to a neuropsychologist (PG) for disability evaluations. These patients were also given multiple measures of cognitive ability, psycho-pathology, and self-reported memory impairment. A single global index was generated for each of these four types of measures. This was accomplished using meta-analytic procedures to calculate effect sizes (Hedges’ g). Effect sizes were expressed as Z score differences within the sample. The Z scores were then averaged within each type of measure to get a single measure for each patient on the cognitive, effort, psycho-pathology, and subjective memory impairment.

Sample Objective neurological indices & diagnoses were also recorded & patients were classified: Psychiatric Patients (n = 107) Dep = 79; Anx =16; Bipolar = 8; Psychotic = 4 Medical Patients (n = 246) Ortho = 77; CFS = 34; Pain/Fibro = 59; Other = 77. Head Injured? (n = 48) without radiological findings documented in medical record. Mild Head Trauma (n = 329) PTA < 24 hrs and positive radiological findings. Definite Traumatic Brain Injury (n = 93) PTA > 24 hrs and positive radiological findings. Neurological Patients (n = 75) Stroke = 21; Aneurysm = 15; MS = 11; Tumor = 8; Epilepsy = 3; Other = 17.

Dependent Measures Overall Test Battery Mean OTBM (N = 43) Verbal Comprehension VC (n = 4) WRAT-III – Read, Spell, & Math WAIS-R VIQ Perceptual Organizational PO (n = 4) Rey CFT – Copy & Recall Judgment of Line Orientation WAIS-R PIQ Executive Functioning EF (n = 6) Wisconsin Card Sort – # Sorted, & Per. Err Category Test - Errors Thurstone Word Fluency Ruff Figure Fluency Gorham’s Proverbs Memory and Learning ML (n = 15) CVLT – Total, Trial 5, SDFR, LDFR, & Rgn Story Recall Test – Imm. & Delayed Recall Word Memory Test – PA, MC, DFR, & LDFR Rey CFT – Delayed FR & Rgn Warrington –Words & Faces Attention & Working Memory AW (n = 8) Trail Making Test – Forms A & B Digit Span – Forward & Backward Visual Memory Span – Forward & Backward CVLT – Trial 1 & List B Psychomotor Speed PS (n = 6) Finger Tapping – Dom. & N’dom. Grip Strength – Dom. & N’dom. Grooved Pegboard – Dom & N’dom.

Symptom Validity SV (N = 5) Computer Assessment Response Bias Total score for all 3 Blocks of trials Word Memory Test (n = 3) Imm. & 30-m Del. Rgn (IR & DR) Consistency CVLT Logit Formula (n = 1) Emotional & Personality Variables (N=18) Beck Depression Inventory (n = 1) MMPI-2 (n = 8) Hs, De, Hy, Pd, Pa, Pt, Sc, Ma Symptom Checklist–90 Revised (n = 9) Som, Oc, Is, Dep, Anx, Hos, Phob, Para, Psych Self Assessment of Memory Memory Complaints Inventory (n = 9) General Memory Problems (GMP) Numeric Information Problem (NIP) Visual-Spatial Problems (VSP) Verbal Memory Problems (VMP) Pain Interferes with Memory (PIM) Memory Interferes with Work (MIW) Impaired Remote Memory (IRM) Amnesia Complex Behavior (ACB) Amnesia Antisocial Behavior (AAB)

Results Correlation between cognitive ability measures as defined by the OTBM and SV measure was .73. On the basis of patients’ performance on the SV measures, they were classified as: Genuine Responders (n = 653; 73%) or Poor Effort (n = 245; 27%). Table of the % Variance shows the Symptom Validity composite index accounted for more variance than any other single domain, as well as any demographic variable and any index of the severity of neurological impairment.

Attention Work Mem. (AW) 52%   Percent Variance Accounted for by Each Domain Mean Z Score in the OTBM. Rank Domain Assess % of Variance 1 Symptom Validity (SV) 53% 2 Attention Work Mem. (AW) 52% 3 Memory & Learning (ML) 49% 4 Perceptual Organ. (PO) 5 Executive Functioning (EF) 41% 6 Verbal Comprehension (VC) 32% 7 Psychomotor Speed (PS) 17% 8 Memory Complaints (Self) 11% 9 Education 10 English as 1st Language 7% 11 Emotional-Personality (EP) 5% 12 Age 4% 13 PTA duration (retrospective) 1% 14 LOC 15 GCS on admission 16 Sex < 1% 17 Positive CT or MRI signs

Discussion The Symptom Validity composite accounted for more variance in cognitive ability tests than did any demographic variables. The Symptom Validity accounts for less variance in the domains of emotion-personality and metamemory than in cognitive ability, but remained the most predictive variable in these domains compared to demographic and acute injury variables. The Word Memory Test – Delayed Recall measure is the best single predictor of poor effort in the Symptom Validity composite. The least predictive measure in the Symptom Validity composite was the CVLT Logit Formula of Millis et al. (1999). Verbal memory measures remained the most vulnerable to symptom exaggeration, followed by Perceptual Organizational tasks and Attentional tasks.