Executive dysfunction in traumatic brain injury: The effects of injury severity and effort on the Wisconsin Card Sorting Test

Transcription

1 This article was downloaded by: [Stephen F Austin State University] On: 25 May 2015, At: 10:17 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Journal of Clinical and Experimental Neuropsychology Publication details, including instructions for authors and subscription information: Executive dysfunction in traumatic brain injury: The effects of injury severity and effort on the Wisconsin Card Sorting Test Jonathan S. Ord a, Kevin W. Greve a b, Kevin J. Bianchini a b & Luis E. Aguerrevere a a University of New Orleans, New Orleans, LA, USA b Jefferson Neurobehavioral Group, Metairie, LA, USA Published online: 29 May To cite this article: Jonathan S. Ord, Kevin W. Greve, Kevin J. Bianchini & Luis E. Aguerrevere (2010) Executive dysfunction in traumatic brain injury: The effects of injury severity and effort on the Wisconsin Card Sorting Test, Journal of Clinical and Experimental Neuropsychology, 32:2, , DOI: / To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the Content ) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at

2 JOURNAL OF CLINICAL AND EXPERIMENTAL NEUROPSYCHOLOGY 2010, 32 (2), NCEN Executive dysfunction in traumatic brain injury: The effects of injury severity and effort on the Wisconsin Card Sorting Test WCST IN TBI Jonathan S. Ord, 1 Kevin W. Greve, 1,2 Kevin J. Bianchini, 1,2 and Luis E. Aguerrevere 1 1 University of New Orleans, New Orleans, LA, USA 2 Jefferson Neurobehavioral Group, Metairie, LA, USA This study examined the persistent effects of traumatic brain injury (TBI) on Wisconsin Card Sorting Test (WCST) performance. Since poor effort can contaminate results in populations with incentive to perform poorly, performance validity was explicitly assessed and controlled for using multiple well-validated cognitive malingering indicators. Participants were 109 patients with mild TBI and 67 patients with moderate-to-severe TBI seen for neuropsychological evaluation at least one year post injury. Patients with diffuse neurological impairment and healthy controls were included for comparison. Results suggested a dose response effect of TBI severity on WCST performance in patients providing good effort; the mild TBI group did not differ from controls while increased levels of impairment were observed in the moderate-to-severe TBI group. Effort during testing had a larger impact on WCST performance than mild or moderate-to-severe TBI. Clinical implications of these findings are discussed. Keywords: Traumatic brain injury; Wisconsin Card Sorting Test; Executive function; Outcome; Performance validity; Effort; Malingering. Impairments in executive function are commonly reported following traumatic brain injury (TBI) and can have a large impact on expected outcome (Cicerone et al., 2000; McDonald, Flashman, & Saykin, 2002). Executive dysfunctions can result in a dramatic loss of overall functionality, such as the ability to work (Sherer et al., 1998) or to form social relationships (Mazaux et al., 1997), regardless of other cognitive abilities (Cicerone et al., 2000). Thus, understanding the relationship between TBI and deficits in executive function is important for both researchers and clinicians working with patients who have suffered a head injury. TBI severity, established using initial injury characteristics and results from neuroimaging, generally provides the most reliable measure of underlying neuropathology (Gaetz, 2004). In fact, many studies have reported a near linear dose response relationship between TBI severity and subsequent neurocognitive deficits (Belanger & Vanderploeg, 2005; Ponsford et al., 2000; Rohling, Meyers, & Millis, 2003; Schretlen & Shapiro, 2003; Sherer, Madison, & Hannay, 2000). These deficits are worst in the acute postinjury stages, and significant recovery is usually seen in the first few months (Alexander, 1995; Lehtonen et al., 2005; Schretlen & Shapiro, 2003). While persistent cognitive deficits are observed in some patients with moderate-to-severe TBI, mild uncomplicated head injuries are not expected to produce persistent cognitive impairments as a result of injury-related neuropathology (Carroll et al., 2004; Iverson, 2005; Schretlen & Shapiro, 2003). Results from this study were presented at the 36th Annual Meeting of the International Neuropsychological Society. Parts of this study were also submitted as a thesis by the first author to the Department of Psychology of the University of New Orleans in partial fulfillment of the requirements for the degree of Master of Science in Psychology. This project is one component of a much larger data collection project. Our research assistants, including Jeffrey Love, Matthew Heinly, Kelly Curtis, and Adrianne Brennan, have been tireless, and their efforts are much appreciated. Address correspondence to Kevin W. Greve, Department of Psychology, University of New Orleans Lakefront, New Orleans, LA 70148, USA ( kgreve@uno.edu) Psychology Press, an imprint of the Taylor & Francis Group, an Informa business DOI: /

3 WCST IN TBI 133 Persistent cognitive impairments that cannot be explained by acute injury characteristics or preexisting factors are most often associated with financial incentive to perform poorly (Belanger, Curtiss, Demery, Lebowitz, & Vanderploeg, 2005; Carroll et al., 2004). Financial incentive has a direct impact on the validity of performance during testing (Bianchini, Curtis, & Greve, 2006). Invalid patient performance can take many forms, from intentional negative response bias to poor effort/ motivation during testing, and can negatively impact measures of cognitive (e.g., Bernard, Houston, & Natoli 1993; Iverson & Binder, 2000), motor (e.g., Greiffenstein, Baker, & Gola, 1994), and sensory functioning (e.g., Green & Iverson, 2001). Green, Rohling, Lees-Haley, and Allen (2001) reported that effort during testing accounted for 53% of variance on neuropsychological measures, and a review of TBI outcome studies by Iverson (2005) reported that performance validity had a larger overall effect on neuropsychological measures (Cohen s d = 1.1) than did mild TBI (Cohen s d = 0.1) or moderate-to-severe TBI (Cohen s d = 0.8). Thus, failure to address issues related to effort could lead to inaccurate conclusions regarding the effects of TBI on cognition (Green, 2007; Iverson, 2005). Despite the consistency of recent findings regarding the effects of TBI on cognitive function, some concerns are still being raised regarding subtle deficits of executive function following uncomplicated mild TBI (Bigler, 2008). The purpose of the present study is to examine the persistent effects of TBI on the Wisconsin Card Sorting Test (WCST; Grant & Berg, 1948; Heaton, 1981; Heaton, Chelune, Talley, Kay, & Curtiss, 1993). The WCST is a widely used measure of executive function (Rabin, Barr, & Burton, 2005) that has been validated in a number of patient populations (see Heaton et al., 1993, for a review). The WCST is considered to be particularly sensitive to the effects of frontal-lobe injury (Heaton et al., 1993) and thus serves as an important indicator of potential executive dysfunctions in patients with TBI. A number of studies have reported persistent deficits in WCST performance following moderate or severe TBI (e.g., Fork et al., 2005; Heaton et al., 1993; Himanen et al., 2005; Millis et al., 2001), and the perseverative measures are typically found to be the most sensitive to brain injury (King, Sweet, Sherer, Curtiss, & Vanderploeg, 2002; Love, Greve, Sherwin, & Mathias, 2003; Millis et al., 2001; Sherer, Nick, Millis, & Novack, 2003). Lehtonen et al. (2005) found that WCST deficits were worst during the acute postinjury stages, and noticeable gains in performance were observed one year postinjury. In mild TBI, some studies have reported small increases in rates of impairment (e.g., Raskin, Mateer, & Tweeten, 1998), especially in the acute postinjury stage (Iverson, Slick, & Franzen, 2000). However, effort during testing has a direct impact on WCST performance (Bernard, McGrath, & Houston, 1996; Greve, Bianchini, Mathias, Houston, & Crouch, 2002a; Greve, Heinly, Bianchini, & Love, 2009; King et al., 2002; Suhr & Boyer, 1999) and should be considered as a possible explanation for observed impairments. Binder, Kelly, Villanueva, and Winslow (2003) reported that mild TBI had no significant impact on WCST perseverative responses when motivation during testing was controlled for using a measure of cognitive performance validity. The present study seeks to add to the literature on the effects of TBI on WCST performance by examining patients with mild and moderate-to-severe TBI while controlling for performance validity. This study replicates parts of Binder et al. s (2003) study and builds upon it by (a) examining WCST performance in detail, (b) controlling for time between injury and evaluation, and (c) assessing performance validity using multiple indicators of cognitive malingering. Examining WCST performance in this manner is expected to provide a more accurate assessment of the relationship between TBI severity and subsequent executive dysfunctions. Participants METHOD Data were obtained from archival records of patients seen for evaluation at a clinical neuropsychology practice in southern Louisiana between 1993 and From an initial pool of 508 available TBI cases, 176 were included by meeting the following criteria: (a) age between 18 and 75 years; (b) at least one year between injury and evaluation; (c) administration of the WCST and at least two of the four performance validity measures discussed below; and (d) no history of severe (i.e., inpatient) neuropsychiatric conditions. Almost all (97%) had incentive to perform poorly, usually in the form of workers compensation (64%) or a personal injury claim (26%). Approximately half of the TBI cases examined in this study were included in two previous studies of WCST internal validity indicators (Greve et al., 2002a; Greve et al., 2009). A set of patients with indications of diffuse neurological impairment (e.g., Alzheimer s or vascular dementia) was also collected to serve as a known dysfunction comparison group. Of 90 available cases, 41 were included for study based on the following criteria: (a) less than 76 years old; (b) at least one score from a standardized measure of memory or general intellectual function below one standard deviation from the mean; (c) no history of traumatic brain injury or focal neurological insults (e.g., a major cerebral vascular accident); and (d) no incentive to perform poorly (e.g., disability or compensation claim). A total of 20 healthy participants matching the approximate demographic distribution of the TBI samples were recruited from the community to serve as a local control group. Institutional Review Board approval was obtained for this study. Each participant was administered the WCST and the Portland Digit Recognition Test (PDRT; Binder, 1993b) in standard fashion and was reimbursed for their time. Scoring below cutoffs (discussed below) on the PDRT would have resulted in exclusion; none were excluded. For all groups, patients older than 75 were excluded because corrected T-scores (Heaton et al., 1993) for these age brackets do not produce enough variability to examine impairment on some WCST variables.

4 134 ORD ET AL. Group classification TBI severity TBI cases were classified as mild or moderate to severe according to initial injury characteristics based on a thorough review of medical records. Injuries were considered mild if they had (a) loss of consciousness (LOC) less than 30 min, (b) Glasgow Coma Scale (GCS) of 13 15, (c) posttraumatic amnesia (PTA) less than 24 hours, (d) no focal neurologic signs, and (e) no abnormalities on neuroimaging attributable to the head injury. Any injury that met one or more of these criteria was classified as moderate to severe. These criteria accord with most diagnostic standards and current research in this field (Alexander, 1995; Peloso et al., 2004). Performance validity Each TBI case was also classified according to the validity of patient performance based on four indicators of cognitive malingering discussed below. A failure on one or more of these measures was considered an indication of poor effort during testing. Thus, patients were included in the good effort group only if they scored above cutoffs on each performance validity measure. Given that participants in the control group did not have incentive to perform poorly, administration of a single measure, the PDRT, was deemed adequate to ensure good effort during testing. Similarly, none of the patients from the diffuse neurological impairment group had incentive to perform poorly, and thus performance validity measures were not administered during the original evaluations. Group summary Classifications resulted in the following groups: (a) patients with a mild TBI who showed good effort during testing (mild-ge; n = 67); (b) patients with a mild TBI who showed poor effort during testing (mild-pe; n = 42); (c) patients with a moderate-to-severe TBI who showed good effort (modsev-ge; n = 46); (d) patients with a moderate-to-severe TBI who showed poor effort (modsev-pe; n = 21); (e) patients with diffuse neurological impairment (neuro; n = 49); and (f) controls (n = 20). Measures Wisconsin Card Sorting Test (WCST; Heaton et al., 1993) The WCST was administered using standard procedures detailed by Heaton et al. (1993) and was scored using commercially available software (Psychological Assessment Resources, 1993). Factor analysis has demonstrated three primary components to WCST performance in both normal and clinical samples: (I) cognitive flexibility and accuracy; (II) problem solving and learning; (III) response maintenance and distractibility (Greve, Brooks, Crouch, Williams, & Rice, 1997; Greve, Ingram, & Bianchini, 1998; Greve et al., 2002c; Greve, Stickle, Love, Bianchini, & Stanford, 2005; Wiegner & Donders, 1999). Thus, seven standard variables were selected to represent the pertinent factors of WCST performance. Factor I abilities were represented by total errors (TE), perseverative responses (PR), and percentage of conceptual level responses (PCLR). Factor II abilities were represented primarily by nonperseverative errors (NPE) and to a lesser extent trials to complete first category (T1C). Factor III abilities were represented by failures to maintain set (FMS). Categories completed (CAT), which primarily loads on Factor I, was also included as an overall measure of strategy development and execution. Age- and education-corrected T-scores from Heaton et al. (1993) were used whenever possible. For the parametric variables (TE, PR, NPE, and PCLR), these corrections were available for full distributions up to three standard deviations from the mean and were thus used in all analyses. For the nonparametric variables (CAT, T1C, FMS), corrections were only available for levels of impairment up to the 16th percentile and thus could only be used in the examination of impairment rates. Portland Digit Recognition Test (PDRT; Binder, 1993b) The PDRT is a commonly used cognitive performance validity measure employing a forced-choice recognition memory format. All patients in the TBI and control groups were administered this measure. Any score below 22 for the easy portion, 20 for the hard portion, or 44 total was considered an indication of poor effort. A number of studies confirm accurate classification of performance validity in patients with TBI at these cutoffs (Bianchini, Mathias, Greve, Houston, & Crouch, 2001; Binder, 1993a; Binder & Kelly, 1996; Greve & Bianchini, 2006). Participants qualifying for the abbreviated administration were considered to be showing good effort based on administration procedures from Binder (1993b) and validation from Doane, Greve, and Bianchini (2005). Test of Memory Malingering (TOMM; Tombaugh, 1996) The TOMM was also used to identify invalid cognitive performance in patients with TBI. Scores on the TOMM were available for 64.8% of examined TBI cases. Any score below 45 on Trial 2 or Retention was considered an indication of poor effort based on recommendations from the manual (Tombaugh, 1996) and classification accuracy from Greve, Bianchini, and Doane (2006). Word Memory Test (WMT; Green, Allen, & Astner, 1996) The WMT was also used to identify invalid cognitive performance in patients with TBI. Scores on the WMT were available for 4% of examined TBI patients. The cutoffs recommended by Green et al. (1996) in the manual were not used due to methodological issues regarding the development of these cutoffs and concern that the original cutoffs may produce an unacceptably

5 WCST IN TBI 135 high level of false positives. Thus, a more conservative cutoff of less than 72.5 on either Immediate or Delayed Recall was chosen to identify poor effort based on classification accuracy data from Greve, Ord, Curtis, Bianchini, and Brennan (2008). Reliable Digit Span (RDS; Greiffenstein et al., 1994) RDS is an internal validity indicator derived from the Digit Span subtest of the Wechsler Adult Intelligence Scale (Revised or Third Edition; Wechsler, 1981, 1997) by summing the longest forward and backward digit spans on which both trials were repeated correctly. RDS was available for all but one examined TBI case. RDS has been validated as an accurate measure of performance validity in a number of studies (Greiffenstein, Gola, & Baker, 1995; Heinly, Greve, Bianchini, Love, & Brennan, 2005; Mathias, Greve, Bianchini, Houston, & Crouch, 2002; Meyers & Volbrecht, 1998), and a score below 7 was considered evidence of poor effort based on these results. Demographics RESULTS Analysis of variance revealed no significant differences in education. Age was only significantly higher Age (years) TABLE 1 Group demographics in the neuro group (p <.05). Chi-square analysis revealed no significant differences in ethnic composition across the groups. A gender difference was observed (p <.05), though the association was relatively weak (Cramer s V =.27). Gender is reported to have no significant effect on WCST performance (Heaton et al., 1993); thus, this difference is not expected to impact analyses. Table 1 presents a breakdown of age, education, gender, and primary ethnicity for each group. TBI characteristics Table 2 presents a summary of basic injury characteristics for the TBI groups. Analysis of variance revealed no significant differences in the length of time between injury and evaluation across the groups although times were generally longer in moderate-tosevere injuries due to a few outliers at the longer end of the spectrum. Glasgow Coma Scale scores were not significantly different between the mild TBI groups or between the moderate-to-severe TBI groups. Note that PTA and LOC were not statistically analyzed due to the difficulty in establishing exact values from medical records. In both mild TBI groups, LOC was typically brief or absent, and reports of PTA were rare. Education (years) Gender Ethnicity Group N M SD M SD % Male % Caucasian Controls Mild-GE Mild-PE Modsev-GE Modsev-PE Neuro N/A a Note. Mild-GE = mild TBI good effort. Mild-PE = mild TBI poor effort. Modsev-GE = moderate-to-severe TBI good effort. Modsev-PE = moderate-to-severe TBI poor effort. Neuro = diffuse neurological impairment. TBI = traumatic brain injury. a Insufficient data were available for analysis. TABLE 2 Basic injury characteristics for the traumatic brain injury groups Mild-GE Mild-PE Modsev-GE Modsev-PE M SD M SD M SD M SD Time since injury (months) Glasgow Coma Scale Note. Mild-GE = mild TBI good effort. Mild-PE = mild TBI poor effort. Modsev-GE = moderate-to-severe TBI good effort. Modsev-PE = moderate-to-severe TBI poor effort. Neuro = diffuse neurological impairment. TBI = traumatic brain injury.

6 136 ORD ET AL. WCST performance Mean scores Analysis of variance indicated significant group differences across TE, PR, PCLR, CAT, and T1C (all with p <.01). Significant differences were not observed on NPE (p =.26) or FMS (p =.65). Pairwise comparisons using Bonferroni corrections indicated that the mild-ge and modsev-ge groups did not differ significantly from controls on any of the examined variables (p >.05). The mild-pe group scored significantly lower (p =.04) than the mild-ge group on TE and marginally lower (p =.05) on PR. The neuro group performed significantly worse than the mild- GE group on most variables. Group means and standard deviations for each WCST variable are presented in Table 3. Effect sizes Effects sizes were examined for Factor I variables (TE, PR, and PCLR) using Cohen s d statistic with pooled variance. Only Factor I variables were examined because (a) they are reported to be the most sensitive to brain injury (Heaton et al., 1993), and (b) they are not hierarchically dependent on other WCST variables. The effects of mild TBI, moderate-to-severe TBI, and diffuse neurological impairment were examined by comparing each corresponding good effort group to the control group. The effect of effort was calculated by taking the average of the effect sizes observed between the good effort and poor effort groups in mild and moderate-to-severe TBI groups, respectively. Averaged across the three examined variables, mild TBI showed essentially no effect on WCST performance (0.05), moderate-to-severe TBI showed a small negative effect on performance (0.09), and diffuse neurological impairment showed a large negative effect (0.71). The average effect of effort (0.42) was considerably higher than the effect of mild or moderate-to-severe TBI. Table 4 presents the effect sizes of each examined variable for TBI, diffuse neurological impairment, and effort. Impairment In addition to comparing mean scores it is also important to examine rates of impairment among the groups to identify potentially subtle differences at lower ranges of the distributions. To facilitate comparisons, levels of impairment on WCST variables were established to correspond with those presented in the manual (Heaton et al., 1993). Note that the manual presents impairment ranges at slightly different levels for the nonparametric variables (CAT, T1C, FMS), and those differences are reflected here. Cumulative frequencies of impairment for each group are presented in Table 5 along with percentages of normative impairment calculated using tables presented by Heaton et al. for both normal and clinical TBI participants (E1 and E2, pp ). As can be seen on Table 5, rates of impairment also showed a dose response relationship with TBI severity. Chi-square analysis revealed no significant differences (all p >.05) between rates of Factor I impairments in the mild- GE and control groups. On PR, a measure considered to be particularly sensitive to the effects of brain injury, the ratio of patients with mild or worse impairment (T-score < TABLE 4 Effect sizes of TBI, diffuse neurological impairment, and effort on WCST Factor I variables Variables Mild TBI a M/S TBI a Neuro a Effort b Total errors Perseverative responses % Conceptual level responses Note. M/S = moderate-to-severe. Neuro = diffuse neurological impairment. TBI = traumatic brain injury. WCST = Wisconsin Card Sorting Test. a Calculated by comparing each corresponding good effort group to the control group. b Average of effect sizes calculated by separate comparisons between the good effort and poor effort groups within each TBI severity. TABLE 3 Group means and standard deviations for examined WCST variables Mild TBI M/S TBI Controls GE PE GE PE Neuro M SD M SD M SD M SD M SD M SD Total errors ab a ab ab ab b Perseverative responses a a a a a a Nonperseverative errors a a a a a a % Conceptual level responses a a a a a a 9.95 Categories completed 4.85 a a a a a b 2.19 Trials to first category a a ab a ab b Failures to maintain set 1.25 a a a a a a 1.21 Note. GE = good effort. M/S = moderate to severe. Neuro = diffuse neurological impairment. PE = poor effort. TBI = traumatic brain injury. WCST = Wisconsin Card Sorting Test. ab Row means with the same letter are not significantly different at alpha <.05.

7 WCST IN TBI 137 TABLE 5 Cumulative percentages of group impairment on WCST variables % Impairment Mild TBI M/S TBI Heaton et al. a Variable T-score Percentile Controls GE PE GE PE Neuro Normal Clinical Total errors < Perseverative responses < Nonperseverative errors < % Conceptual level responses < Categories completed Trials to first category Failures to maintain set Note. GE = good effort. M/S = moderate-to-severe. Neuro = diffuse neurological impairment. PE = poor effort. TBI = traumatic brain injury. WCST = Wisconsin Card Sorting Test. a Calculated using norms presented by Heaton et al. (1993). 40) relative to controls (i.e., the likelihood ratio) was 1.2 for mild-ge patients (95% confidence interval, CI = 0.4 to 3.8), 2.3 for modsev-ge patients (95% CI = 0.8 to 7.1), and 2.9 for neuro patients (95% CI = 1.0 to 8.5). Interestingly, the relative likelihood of impairment in the mild-pe group (3.2; 95% CI = 1.1 to 9.4) was slightly higher than the rate observed in the modsev-pe group (2.9; 95% CI = 0.9 to 9.1). DISCUSSION Executive dysfunction is often reported following TBI, and assessment of these deficits can be complicated by external incentives to perform poorly. The present study examined the persistent effects of mild and moderate-to-severe TBI on WCST scores while controlling for the validity of patient performance during testing. Overall, results suggested a dose response relationship between TBI severity and deficits on the WCST in patients providing good effort during testing. Patients with mild TBI showed essentially no measurable deficits in WCST performance while patients with moderate-to-severe TBI showed increased levels of impairment on some WCST indices. Effort during testing was found to have a larger impact on WCST performance than did mild or moderate-to-severe TBI. Results from this study were consistent with similar studies that have examined the effects of TBI while considering the effects of performance validity (e.g., Binder et al., 2003; Rohling et al., 2003).

8 138 ORD ET AL. TBI-related impairment Of particular interest are mild uncomplicated head injuries showing impairment on the WCST. Long-term impairments of any kind are not expected as a persistent neurological effect of mild TBI (Alexander, 1995; Binder et al., 2003; Carroll et al., 2004; Iverson, 2005), and the lack of group differences noted in this study argues, again, against neurological causality of mild TBI for these impaired-level scores. Mean T-scores for the mild- GE group were slightly lower than WCST norms presented by Heaton et al. (1993); however, this small disparity in scores was also present in the locally matched control group and might be expected given the above average general intellectual function of the Heaton et al. control group (mean full-scale intelligence quotient, FSIQ = 117). In comparison, moderate-to-severe TBI had a larger impact on WCST performance. Mean scores were comparable to those of controls and those reported by Lehtonen et al. (2005) for postacute TBI patients with focal injuries. However, deficits resulting from moderate-to-severe TBI were more apparent when observing relatively higher rates of impairment, especially for indices of perseveration. Rates of impairment were in general agreement with those reported by Heaton et al. (1993) for the clinical TBI groups. It should be mentioned as a limitation that moderate-to-severe TBI cases were not separately analyzed according to lesion location when focal pathology was present. WCST considerations While the WCST is the most used and perhaps best validated measure of executive function, many issues are still present that complicate both individual evaluations and group comparisons. Despite indices on the WCST often being presented as independent measures of performance, they are in fact dependent on each other and hierarchical in nature (Greve et al., 2002c). As an example, patients who score at the lowest levels on PR often score at the highest levels on NPE. Patients display this pattern because these measures are exclusive; if too many perseverative errors are made then the nonperseverative variable has nothing left to measure. Another example is FMS, which can only be measured if patient performance is good enough to produce consecutive runs of at least five responses. This is not to say that variables such as NPE and FMS are of no use, just that they are not sensitive measures of impairment, especially in patients showing perseveration. Group comparisons are particularly difficult for these higher factor variables as the large variability seen in WCST performance can overwhelm the low sensitivity of these measures. Thus, when examining impairments in a group study, WCST performance serves primarily as a measure of perseveration and associated Factor I processes such as mental flexibility and response to feedback. This is partly due to the hierarchical nature of the measures, which makes it difficult to measure higher functions when perseveration is present, and partly due to the nature of the administration, which creates a situation that is very conducive to eliciting perseveration. This has been reflected in previous literature, which has reported WCST measures of perseveration to be the most sensitive to brain injury (Heaton et al., 1993) and to account for the majority of variance in factor analyses (Greve et al., 1998; Greve et al., 2005). Results from this study supported these findings as moderate-to-severe TBI, diffuse neurological impairment, and effort all had a much larger effect on Factor I measures than on Factor II (NPE) or Factor III (FMS) measures. Performance validity and measures of executive function Results from this and other studies demonstrate that patients who show indications of poor effort/ malingering are much more likely to perform in the impaired range on cognitive measures (Green et al., 2001). However, the average effect of poor effort observed in this study across Factor I scores (Cohen s d =.42) was considerably smaller than the average reported effect size of malingering on neuropsychological measures (Cohen s d = 1.1; Iverson, 2005). This lower observed effect for poor effort may be due to the complexity of the WCST. Performance on the WCST is dependent on a number of factors including the patient s ability to understand and perform on the task and the chosen malingering strategy. Depending on these factors, poor effort can produce very different patterns across WCST variables. For example, a high-functioning patient intentionally avoiding too many consecutive correct responses will show a completely different effort effect than a low-functioning patient who does not even attempt to form a working strategy. What this suggests is that studies such as this one, which look at group scores in a linear fashion, are likely underestimating the true effect that poor motivation and effort have on individual WCST scores. Limitations Several methodological limitations regarding this study are important to mention. First, these samples represent populations of patients who are being seen for neuropsychological evaluation at least one year postinjury, with most being involved in litigation or workers compensation cases. Of all persons who suffer a TBI, especially at the mild end of the spectrum, these cases represent a relatively small subpopulation of patients who are still reporting symptoms one year postinjury. As such, the rates of impairment observed in this study are likely to be higher than in the TBI population at large. In addition, the relatively small size of these groups should be considered when interpreting results at the extreme ranges of impairment where low frequencies are expected, especially considering the large natural variability in WCST scores. Another consideration is that the WCST may be prone to practice effects (Basso, Bornstein, & Lang, 1999; Greve

9 WCST IN TBI 139 et al., 2002b), and it was not possible to gauge how many patients in these samples may have been impacted by previous exposure to the test. Finally, applying only conservative cognitive malingering cutoffs to classify poor effort may fail to identify patients with more complex psychosocial complications that could potentially impact motivation and resulting WCST validity. Further studies addressing these limitations may be useful. SUMMARY The results of this study suggest a dose response relationship between TBI severity and subsequent deficits in WCST performance in patients providing good effort during testing. At 12+ months postinjury, mild TBI does not have a measurable impact on related executive functions while moderate-to-severe TBI does increase the likelihood of deficits. Effort during testing had a larger effect on WCST performance than did mild or moderate-to-severe TBI. The results of this study, along with other recent studies of deficits following TBI, continue to demonstrate the need to consider factors related to performance validity when examining impairments following compensable injuries. Original manuscript received 3 December 2008 Revised manuscript accepted 1 March 2009 First published online 29 May 2009 REFERENCES Alexander, M. P. (1995). Mild traumatic brain injury: Pathophysiology, natural history, and clinical management. Neurology, 45, Basso, M. R., Bornstein, R. A., & Lang, J. M. (1999). Practice effects on commonly used measures of executive function across twelve months. The Clinical Neuropsychologist, 13, Belanger, H. G., Curtiss, G., Demery, J. A., Lebowitz, B. K., & Vanderploeg, R. D. (2005). Factors moderating neuropsychological outcomes following mild traumatic brain injury: A meta-analysis. Journal of the International Neuropsychological Society, 11, Belanger, H. G., & Vanderploeg, R. D. (2005). The neuropsychological impact of sports-related concussion: A metaanalysis. Journal of the International Neuropsychological Society, 11, Bernard, L. C., Houston, W., & Natoli, L. (1993). Malingering on neuropsychological memory tests: Potential objective indicators. Journal of Clinical Psychology, 49, Bernard, L. C., McGrath, M. J., & Houston, W. (1996). The differential effects of simulating malingering, closed head injury, and other CNS pathology on the Wisconsin Card Sorting Test: Support for the pattern of performance hypothesis. Archives of Clinical Neuropsychology, 11, Bianchini, K. J., Curtis, K. L., & Greve, K. W. (2006). Compensation and malingering in traumatic brain injury: A dose response relationship? The Clinical Neuropsychologist, 20, Bianchini, K. J., Mathias, C. W., Greve, K. W., Houston, R. J., & Crouch, J. A. (2001). Classification accuracy of the Portland Digit Recognition Test in traumatic brain injury. The Clinical Neuropsychologist, 15, Bigler, E. D. (2008). Neuropsychology and clinical neuroscience of persistent post-concussive syndrome. Journal of the International Neuropsychological Society, 14, Binder, L. M. (1993a). Assessment of malingering after mild head trauma with the Portland Digit Recognition Test. Journal of Clinical and Experimental Neuropsychology, 15, Binder, L. M. (1993b). Portland Digit Recognition Test Manual Second Edition. Portland, OR: Author. Binder, L. M., & Kelly, M. P. (1996). Portland Digit Recognition Test performance by brain dysfunction patients without financial incentives. Assessment, 3, Binder, L. M., Kelly, M. P., Villanueva, M. R., & Winslow, M. M. (2003). Motivation and neuropsychological test performance following mild head injury. Journal of Clinical and Experimental Neuropsychology, 25, Carroll, L. J., Cassidy, J. D., Peloso, P. M., Borg, J., von Holst, H., Holm, L., et al. (2004). Prognosis for mild traumatic brain injury: Results of the WHO Collaborating Centre Task Force on Mild Traumatic Brain Injury. Journal of Rehabilitation Medicine, 43(Suppl.), Cicerone, K. D., Dahlberg, C., Kalmar, K., Langenbahn, D. M., Malec, J. F., Bergquist, T. F., et al. (2000). Evidence-based cognitive rehabilitation: Recommendations for clinical practice. Archives of Physical Medicine and Rehabilitation, 81, Doane, B. M., Greve, K. W., & Bianchini, K. J. (2005). Agreement between the abbreviated and standard Portland Digit Recognition Test. The Clinical Neuropsychologist, 19, Fork, M., Bartels, C., Ebert, A. D., Grubich, C., Synowitz, H., & Wallesch, C. W. (2005). Neuropsychological sequelae of diffuse traumatic brain injury. Brain Injury, 19, Gaetz, M. (2004). The neurophysiology of brain injury. Clinical Neurophysiology, 115, Grant, D. A., & Berg, E. A. (1948). A behavioral analysis of degree of reinforcement and ease of shifting to new responses in a Weigl type card sorting problem. Journal of Experimental Psychology, 38, Green, P. (2007). The pervasive influence of effort on neuropsychological tests. Physical Medicine and Rehabilitation Clinics of North America, 18, Green, P., Allen, I., & Astner, K. (1996). Manual for Computerized Word Memory Test. Durham, NC: CogniSyst. Green, P., & Iverson, G. L. (2001). Effects of injury severity and cognitive exaggeration on olfactory deficits in head injury compensation claims. NeuroRehabilitation, 16, Green, P., Rohling, M. L., Lees-Haley, P. R., & Allen, L. M., III. (2001). Effort has a greater effect on test scores than severe brain injury in compensation claimants. Brain Injury, 15, Greiffenstein, M. F., Baker, W. J., & Gola, T. (1994). Validation of malingered amnesic measures with a large clinical sample. Psychological Assessment, 6, Greiffenstein, M. F., Gola, T., & Baker, J. (1995). MMPI-2 validity scales versus domain specific measures in detection of factitious traumatic brain injury. The Clinical Neuropsychologist, 9, Greve, K. W., & Bianchini, K. J. (2006). Classification accuracy of the Portland Digit Recognition Test in traumatic brain injury: Results of a known-groups analysis. The Clinical Neuropsychologist, 20, Greve, K. W., Bianchini, K. J., & Doane, B. M. (2006). Classification accuracy of the Test of Memory Malingering in traumatic brain injury: Results of a known-groups analysis. Journal of Clinical and Experimental Neuropsychology, 28, Greve, K. W., Bianchini, K. J., Mathias, C. W., Houston, R. J., & Crouch, J. A. (2002a). Detecting malingered performance with the Wisconsin Card Sorting Test: A preliminary investigation in traumatic brain injury. The Clinical Neuropsychologist, 16, Greve, K. W., Brooks, J., Crouch, J. A., Williams, M. C., & Rice, W. J. (1997). Factorial structure of the Wisconsin Card Sorting Test. British Journal of Clinical Psychology, 36, Greve, K. W., Heinly, M. T., Bianchini, K. J., & Love, J. M. (2009). Malingering detection with the Wisconsin Card

10 140 ORD ET AL. Sorting Test in mild traumatic brain injury. The Clinical Neuropsychologist, 23, Greve, K. W., Ingram, F., & Bianchini, K. J. (1998). Latent structure of the Wisconsin Card Sorting Test in a clinical sample. Archives of Clinical Neuropsychology, 13, Greve, K. W., Love, J. M., Sherwin, E., Mathias, C. W., Houston, R. J., & Brennan, A. (2002b). Temporal stability of the Wisconsin Card Sorting Test in a chronic traumatic brain injury sample. Assessment, 9, Greve, K. W., Love, J. M., Sherwin, E., Mathias, C. W., Ramzinski, P., & Levy, J. (2002c). Wisconsin Card Sorting Test in chronic severe traumatic brain injury: Factor structure and performance subgroups. Brain Injury, 16, Greve, K. W., Ord, J., Curtis, K. L., Bianchini, K. J., & Brennan, A. (2008). Detecting malingering in traumatic brain injury and chronic pain: A comparison of three forced-choice symptom validity tests. The Clinical Neuropsychologist, 22, Greve, K. W., Stickle, T. R., Love, J. M., Bianchini, K. J., & Stanford, M. S. (2005). Latent structure of the Wisconsin Card Sorting Test: A confirmatory factor analytic study. Archives of Clinical Neuropsychology, 20, Heaton, R. K. (1981). Wisconsin Card Sorting Test manual. Odessa, FL: Psychological Assessment Resources. Heaton, R. K., Chelune, G. J., Talley, J. L., Kay, G. G., & Curtiss, G. (1993). Wisconsin Card Sorting Test manual: Revised and expanded. Odessa, FL: Psychological Assessment Resources. Heaton, R. K., & PAR Staff. (1993). Wisconsin Card Sorting Test: Computer Version 3 [computer software]. Odessa, FL: Psychological Assessment Resources. Heinly, M. T., Greve, K. W., Bianchini, K. J., Love, J. M., & Brennan, A. (2005). WAIS digit span-based indicators of malingered neurocognitive dysfunction: Classification accuracy in traumatic brain injury. Assessment, 12, Himanen, L., Portin, R., Isoniemi, H., Helenius, H., Kurki, T., & Tenovuo, O. (2005). Cognitive functions in relation to MRI findings 30 years after traumatic brain injury. Brain Injury, 19, Iverson, G. L. (2005). Outcome from mild traumatic brain injury. Current Opinion in Psychiatry, 18, Iverson, G. L., & Binder, L. M. (2000). Detecting exaggeration and malingering in neuropsychological assessment. The Journal of Head Trauma Rehabilitation, 15, Iverson, G. L., Slick, D. J., & Franzen, M. D. (2000). Clinical normative data for the WCST-64 following uncomplicated mild head injury. Applied Neuropsychology, 7, King, J. H., Sweet, J. J., Sherer, M., Curtiss, G., & Vanderploeg, R. D. (2002). Validity indicators within the Wisconsin Card Sorting Test: Application of new and previously researched multivariate procedures in multiple traumatic brain injury samples. The Clinical Neuropsychologist, 16, Lehtonen, S., Stringer, A. Y., Millis, S., Boake, C., Englander, J., Hart, T., et al. (2005). Neuropsychological outcome and community re-integration following traumatic brain injury: The impact of frontal and non-frontal lesions. Brain Injury, 19, Love, J. M., Greve, K. W., Sherwin, E., & Mathias, C. (2003). Comparability of the standard WCST and WCST-64 in traumatic brain injury. Applied Neuropsychology, 10, Mathias, C. W., Greve, K. W., Bianchini, K. J., Houston, R. J., & Crouch, J. A. (2002). Detecting malingered neurocognitive dysfunction using the reliable digit span in traumatic brain injury. Assessment, 9, Mazaux, J. M., Masson, F., Levin, H. S., Alaoui, P., Maurette, P., & Barat, M. (1997). Long-term neuropsychological outcome and loss of social autonomy after traumatic brain injury. Archives of Physical Medicine and Rehabilitation, 78, McDonald, B. C., Flashman, L. A., & Saykin, A. J. (2002). Executive dysfunction following traumatic brain injury: Neural substrates and treatment strategies. NeuroRehabilitation, 17, Meyers, J. E., & Volbrecht, M. (1998). Validation of reliable digits for detection of malingering. Assessment, 5, Millis, S. R., Rosenthal, M., Novack, T. A., Sherer, M., Nick, T. G., Kreutzer, J. S., et al. (2001). Long-term neuropsychological outcome after traumatic brain injury. The Journal of Head Trauma Rehabilitation, 16, Peloso, P. M., Carroll, L. J., Cassidy, J. D., Borg, J. R., von Holst, H., Holm, L., et al. (2004). Critical evaluation of the existing guidelines on mild traumatic brain injury. Journal of Rehabilitation Medicine, 43(Suppl.), Ponsford, J., Willmott, C., Rothwell, A., Cameron, P., Kelly, A. M., Nelms, R., et al. (2000). Factors influencing outcome following mild traumatic brain injury in adults. Journal of the International Neuropsychological Society, 6, Rabin, L. A., Barr, W. B., & Burton, L. A. (2005). Assessment practices of clinical neuropsychologists in the United States and Canada: A survey of INS, NAN, and APA Division 40 members. Archives of Clinical Neuropsychology, 20, Raskin, S. A., Mateer, C., & Tweeten, R. (1998). Neuropsychological assessment of individuals with mild traumatic brain injury. The Clinical Neuropsychologist, 12, Rohling, M. L., Meyers, J. E., & Millis, S. R. (2003). Neuropsychological impairment following traumatic brain injury: A dose response analysis. The Clinical Neuropsychologist, 17, Schretlen, D. J., & Shapiro, A. M. (2003). A quantitative review of the effects of traumatic brain injury on cognitive functioning. International Review of Psychiatry, 15, Sherer, M., Bergloff, P., Levin, E., High, W. M., Jr., Oden, K. E., & Nick, T. G. (1998). Impaired awareness and employment outcome after traumatic brain injury. Journal of Head Trauma Rehabilitation, 13, Sherer, M., Madison, C. F., & Hannay, H. J. (2000). A review of outcome after moderate and severe closed head injury with an introduction to life care planning. The Journal of Head Trauma Rehabilitation, 15, Sherer, M., Nick, T. G., Millis, S. R., & Novack, T. A. (2003). Use of the WCST and the WCST-64 in the assessment of traumatic brain injury. Journal of Clinical and Experimental Neuropsychology, 25, Suhr, J. A., & Boyer, D. (1999). Use of the Wisconsin Card Sorting Test in the detection of malingering in student simulator and patient samples. Journal of Clinical and Experimental Neuropsychology, 21, Tombaugh, T. (1996). Test of Memory Malingering manual. New York: MultiHealth Systems. Wechsler, D. (1981). Wechsler Adult Intelligence Scale Revised. New York: Psychological Corporation. Wechsler, D. (1997). Wechsler Adult Intelligence Scale Third Edition. San Antonio, TX: Psychological Corporation. Wiegner, S., & Donders, J. (1999). Performance on the Wisconsin Card Sorting Test after traumatic brain injury. Assessment, 6,