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Performance Validity in Deep Brain Stimulation Candidates

Performance Validity in Deep Brain Stimulation Candidates Objective: Effort and motivation are important factors that influence performance on neuropsychological tests. Performance validity tests (PVT) have not been investigated in a sample of individuals who are at risk for cognitive decline and are presumably highly motivated to do well. The aim of the current study is to investigate performance validity in individuals with Parkinson’s disease and essential tremor who are being considered for deep brain stimulation (DBS) surgery. Methods: Thirty DBS surgical candidates underwent neuropsychological evaluation including completion of the Word Memory Test (WMT) as well as embedded PVTs. Results: Sixteen DBS candidates (53.3%) obtained a passing WMT score, 11 patients (36.6%) obtained scores in the “caution” range, and three patients (10%) produced failing scores. None of the patients scored below an 82.5% on the first three WMT subtests. Conclusions: This pilot study is the first to describe PVT in DBS candidates and in a presumed highly motivated, older, and cognitively at-risk sample. Keywords: Dementia; Movement disorders; Elderly; Performance validity testing; Parkinson’s disease Introduction An individual’s engagement during testing can be influenced by a wide range of external and internal factors. Insufficient effort or invalid performance, specifically, has been strongly related to neuropsychological test results (Green, 2007). For this reason, the American Academy of Clinical Neuropsychology (AACN) and the National Academy of Neuropsychology (NAN) recommend to objectively measure non-credible performance through stand-alone and embedded performance validity tests (PVTs) during all neuropsychological evaluations (Bush et al., 2005; Heilbronner et al. 2009). Performance on both PVTs and cognitive measures are not only affected by intrinsic motivational factors to perform a certain way, but may also be influenced by cognitive dysfunction as observed in individuals with neurodegenerative disease (Green, Montijo, & Brockhaus, 2011). While performance validity studies have been applied to a wide range of samples considered at risk for invalid perfor- mance, only a few studies have assessed performance validity in “motivated” samples. Flaro, Green, and Robertson (2007) examined three different groups of individuals: mild to moderate traumatic brain injury (TBI) claimants with external incen- tives to perform poorly for financial compensation, individuals with a strong incentive to perform well who were going through custody battles, and a group of individuals with little to no incentive to do poorly or well (i.e., children with impairment from various medical conditions). The study used the Word Memory Test (WMT), one of the most widely used PVTs (Hartman, 2002). Results from this study demonstrated that the mild TBI claimant group failed the WMT at a higher rate than the motivated and neutral groups. Importantly, the passing rate of parents seeking custody of their children (moti- vated group) was 98.3% versus only 60% in the mild TBI group. In a similar and more recent study by Green and Flaro © Published by Oxford University Press 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US. doi:10.1093/arclin/acx081 Advance Access publication on 18 September 2017 Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 509 (2015), the authors found that adults with intellectual deficits who were involved with custody battles and hence motivated to do well, did not fail PVTs any more often than adults of higher intelligence. The comparison group of adults with intellectual deficits who had an external reason to perform poorly scored significantly lower on these tests. Similarly, Chafetz, Prentkowski, and Rao (2011) examined intrinsic motivation by comparing PVTs among three low functioning groups: social security claimants, rehabilitation service claimants who are seeking to work, and parents who are seeking reunification with their children from the Department of Family and Child Services. Results showed that all the parents seeking reunification with their children passed the PVTs. The highest failure rate was found for the social security claimants. Overall, these studies highlight the affect of intrinsic motivation to do well on PVTs in a variety of populations. It is also important to note that diseases associated with aging or other neurological illness may negatively influence PVTs. Dean, Victor, Boone, Philpott, and Hess (2009) examined performance validity indices derived from multiple tests (e.g., WAIS-III/WAIS-R Digit Span and Vocabulary, Dot Counting Test, Warrington Recognition Memory Test-Words, WMS-III Logical Memory) in a heterogeneous dementia sample and reported test specificities falling within the range of 30%–70%. Another study examined the specificity of the WAIS-IV Digit Span derived embedded validity measures (i.e., Reliable Digit Span) in a homogenous dementia sample of patients with probable Alzheimer’s disease, revealing high false positive rates and bringing into question the utility of set cut-offs with individuals exhibiting moderate to severe memory impairment (Kiewel, Wisdom, Bradshaw, Pastorek, & Strutt, 2012). The research regarding specificity of more widely used stand-alone PVTs, such as the WMT and the Medical Symptom Validity Test (MSVT), have demonstrated variable findings. For example, in a sample of 63 older patients examined in a memory disorders clinic, 42% performed below recommended threshold scores on the MSVT (Howe, Anderson, Kaufman, Sachs, & Loring, 2007). However, when considering the “genuine memory impairment profile” (GMIP), a specificity of greater than 90% was obtained (Howe & Loring, 2009). Similarly, Green and colleagues (2011) reported the WMT GMIP to have a very high specificity rate of 98.4% in possible MCI and probable dementia. Overall, the literature has focused on specificity rates of PVTs in dementia samples but it has not considered the influence of intrinsic motivation to perform well on these measures. In the current study, we conceptualized a group of patients with Parkinson’s disease (PD) and essential tremor (ET) that were being evaluated for deep brain stimulation surgery (DBS) as a group that has an intrinsic motivation to perform well. Neuropsychological assessments are routinely conducted as part of comprehensive evaluations for candidacy for DBS with good cognitive performance further endorsing a patient’s candidacy and dementia serving as a contraindication for the sur- gery. Therefore, it may be assumed that these patients wanting to undergo surgery to alleviate their symptoms are motivated to do well on neuropsychological measures, resulting in low failure rates on PVTs. This study will investigate performance validity, assessed via the WMT, in PD and ET DBS surgery candidates, who are at increased risk for cognitive impairment and who are presumably intrinsically motivated to perform well. Methods Participants Thirty DBS candidates (28 men; two women) from the Neurology departments of the Michael E. DeBakey VA Medical Center and Baylor College of Medicine underwent neuropsychological evaluations including completion of the Word Memory Test (WMT). The observed male predominance of the sample was expected given that only 10% of the Veteran pop- ulation are women. The sample consisted of 20 participants with PD and 10 with ET (M = 65.9, SD = 8.3; range = age age 48–90). The average years of education of the sample was 13.2 (SD = 2.3; range = 8–18). Diagnostically, 15 participants did not meet criteria for a neurocognitive disorder, while two participants were diagnosed with PD-Dementia, and 13 were diag- nosed with PD-Mild Cognitive Impairment (PD-MCI). Of those, three individuals met criteria for amnestic PD-MCI and 10 patients met criteria for non-amnestic PD-MCI. For patients with PD, the median Hoehn and Yahr disease stage was 2.5 (range = 0–5). Based on the Unified Parkinson’s Disease Rating Scale (UPDRS), the mean motor score for participants with PD was 22.5 (SD = 14.3). Only six participants with essential tremor had motor data available from the Essential Tremor Rating Assessment Scale (TETRAS; M = 30.9, SD = 2.0). Procedures The Word Memory Test was administered to patients at the beginning of the neuropsychological evaluation. For any fail- ing scores on the easy subtests (IR, Immediate Recognition; DR, Delayed Recognition; CN, Consistency), the GMIP was cal- culated based on the average difference between easy and hard WMT subtests (MC, Multiple Choice; PA, Paired Associates; Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 510 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 FR, Free Recall) (Green, Lees-Haley, & Allen, 2003). Given the clinical nature of the assessment, there was some variability in measures completed by the patients. The assessment included the following measures: Mini Mental Status Examination (MMSE; n = 30), Beck Depression Inventory-II (BDI-II; n = 30), Wechsler Adult Intelligence Scale-IV (WAIS-IV) Digit Span (n = 28), Rey Auditory Verbal Learning Test (RAVLT, n = 22), Hopkins Verbal Learning Test-Revised (HVLT-R; n = 7), Wechsler Memory Scale-IV (WMS-IV) Logical Memory (n = 29), Brief Visuospatial Memory Test-Revised (BVMT-R; n = 29), Trail Making Test A (TMT-A; n = 30), Trail Making Test B (TMT-B; n = 30), Symbol DigitModalityTest(SDMT)Oral(n = 28) and Written (n = 26), Boston Naming Test (BNT; n = 29), Verbal Fluency (FAS; n = 29 & Animals = 28), and the Word Memory (WMT; n = 30). The BDI, SDMT, WAIS-IB DS, HVLT-R, WMS-IV LM, and BVMT-R were scored and normed with the normative data provided on their respective manuals. The Geffen, Geffen, and Bishop (1997) normativedatawas used forthe RAVLT. The Revised Comprehensive Norms for an Expanded Halstead-Reitan Battery Heaton norms were used to score the TMT, BNT, FAS, and Animals (Heaton, Miller, Taylor, & Grant, 2004). The following embedded measures of performance validity were also examined: reliable digit span (RDS) with a cut score <6(Kiewel et al., 2012); Animals and FAS verbal fluency T-scores with cut scores of <33 and <30, respectively (Sugarman & Axelrod, 2015); ratio of TMT B:A with a cut-score of <1.50 (Iverson, Lange, Green, & Franzen, 2002); RAVLT recognition combination equation with a cut-score of <12 (Boone, Lu, & Wen, 2005); BVMT-R retention percentage with a cut-score of <58% (Sawyer, Testa, & Dux, 2017); and the HVLT-R Recognition Discrimination Index of a cut-score of <5(Sawyer et al., 2017). Results Participant’s scores can be found in Table 1. Using standardized cut scores (Green, 2005), 90% of the patients passed the WMT based on their scores on the easy subtests. Specifically, a total of 16 DBS candidates obtained a WMT “pass” score (>90%), whereas 11 patients obtained scores in the “caution” range (scores between 83% and 90%, considered passing), and Table 1. Word Memory Test Performance Movement disorder Cognitive diagnosis Age Edu. IR DR CN MC PA FR ET None 48.0 15.0 100.0 100.0 100.0 100.0 100.0 55.0 ET None 90.0 11.0 100.0 97.5 97.5 90.0 90.0 17.5 ET MCI-EF 56.0 13.0 100.0 92.5 92.5 60.0 65.0 45.0 ET** MCI-PS&EF 64.0 12.0 100.0 87.5 87.5 75.0 65.0 32.5 ET* None 74.0 12.0 100.0 82.5 82.5 80.0 65.0 25.0 ET None 75.0 11.0 97.5 92.5 95.0 70.0 80.0 35.0 ET** None 69.0 12.0 95.0 90.0 90.0 70.0 70.0 35.0 ET** MCI-EF 67.0 12.0 92.5 95.0 87.5 55.0 50.0 35.0 ET** None 66.0 14.0 92.5 90.0 87.5 55.0 60.0 35.0 ET* MCI-EF 67.0 13.0 87.5 95.0 82.5 35.0 40.0 17.5 PD None 62.0 16.0 100.0 100.0 100.0 100.0 100.0 55.0 PD None 59.0 16.0 100.0 97.5 97.5 100.0 95.0 67.5 PD PD-Dementia 71.0 14.0 100.0 97.5 97.5 100.0 75.0 35.0 PD MCI-Amnestic 69.0 11.0 100 97.5 97.5 75.0 65.0 37.5 PD None 61.0 10.0 100 95.0 95.0 90.0 85.0 35.0 PD MCI-Amnestic 69.0 16.0 97.5 100.0 97.5 95.0 85.0 55.0 PD None 64.0 18.0 97.5 95.0 97.5 75.0 65.0 32.5 PD** MCI-EF 67.0 16.0 97.5 92.5 90.0 100.0 95.0 45.0 PD** MCI-EF 64.0 12.0 97.5 90.0 87.5 60.0 70.0 37.5 PD* MCI-Amnestic 67.0 16.0 97.5 82.5 85.0 80.0 80.0 45.0 PD None 57.0 12.0 95.0 100.0 95.0 100.0 95.0 47.5 PD None 61.0 12.0 95.0 100.0 95.0 100.0 90.0 77.5 PD MCI-EF 66.0 12.0 95.0 97.5 97.5 70.0 70.0 55.0 PD MCI-multi-domain 48.0 12.0 95.0 95.0 95.0 85.0 75.0 37.5 PD None 78.0 8.0 95.0 95.0 95.0 45.0 40.0 37.5 PD** None 67.0 16.0 92.5 97.5 90.0 75.0 80.0 47.5 PD** PD-Dementia 69.0 12.0 92.5 87.5 90.0 50.0 40.0 22.5 PD** MCI-EF 74.0 14.0 87.5 92.5 85.0 80.0 65.0 42.5 PD** MCI-EF 61.0 12.0 85.0 97.5 87.5 75.0 65.0 25.0 PD** None 66.0 16.0 85.0 90.0 85.0 60.0 60.0 32.5 Note:PD = Parkinson’s disease; ET = essential tremor; MCI = mild cognitive impairment; EF = executive function; IR = immediate recall; D = delayed recall; CN = consistency; MC = multiple choice; PA = paired associates; FR = free recall; PS = processing speed.*Fail Score (bold); **Caution Score (italic). Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 511 Table 2. Frequency of patients who failed embedded measures of performance validity WMT test results Embedded measures Pass Caution Fail RDS (<6) 0 0 1 BVMT PR (<58%) 0 1 0 RAVLT EE (<12) 7 7 1 HVLT-R RDI (<5) 1 0 0 TMT B:A Ratio (<1.50) 0 1 0 FAS (T < 30) 0 1 0 Animals (T < 33) 0 1 0 Note: RDS = Reliable Digit Span; BVMT PR = Brief Visual Memory Test Percent Retention; RAVLT EE = Rey Auditory Verbal Learning Test Effort Equation; HVLT-R RDI = Hopkins Verbal Learning Test-Revised Recognition Discrimination Index; TMT B:A = Trail Making Test Ratio of B:A; WMT = Word Memory Test. three patients produced failing scores (<82.5%). Two of the three WMT failures met the 30 point GMIP criteria. Of these pa- tients, one had a diagnosis of PD-MCI, and one did not meet criteria for a neurocognitive disorder. Computing classification accuracy based on embedded PVTs was not appropriate considering the small sample size of the study; therefore, the results of these measures were only qualitatively examined. The frequencies of pass and failures of all embedded PVTs examined can be found in Table 2. Broadly, there was no clear pattern with the embedded performance validity measures and participants appeared equally likely to fail an embedded PVT as opposed to the WMT. However, it was noteworthy that 50% of the sample failed the RAVLT effort equation. The three participants that scored in the failure range of the WMT had variable performance on the embedded measures. One of the participants, who was not diagnosed with a cognitive disorder, scored below cut scores only on the RDS and the RAVLT equation. The second participant in this cate- gory, who was diagnosed with amnestic MCI, scored below expectation only on the RAVLT embedded measure. Lastly, the third participant who diagnosed with MCI-non-amnestic, did not score below cut scores on any embedded PVTs. Statistical analyses of the neuropsychological data were not appropriate given the small sample size of this pilot study (Table 3). Nevertheless, qualitative observations about the average scores can be made regarding the performance of each group. Performance on measures of brief attention, visual scanning, executive function, language, contextual verbal memory, and visual memory was low average to average across the three groups. Depression scores were highest for the “caution” group. On a measure of written processing speed, the “caution” group performed in the mildly impaired range compared to average performances in the other groups. There were three participants who scored 82.5 (DR & CN; see Table 1), which is considered the highest threshold for a failure and no participants scored below 82.5. v Discussion This proof of concept study examined PVTs in a sample of motivated pre-surgical DBS candidates who are experiencing cognitive decline or are at risk of future decline given their neurodegenerative diagnoses. Although half of the participants were diagnosed with a neurocognitive disorder, it is presumed they were motivated to have the surgery and improve their quality of life, resulting in intrinsic motivation to perform well on the WMT and cognitive assessment. Previous research investigating the use of PVTs in dementia and mild cognitive impairment samples resulted in conflicting results (Green et al., 2011; Walter, Morris, Swier-Vosnos, & Pliskin, 2014). However, this study demonstrates high passing rates (90%) of a stand-alone PVT in a presumed highly motivated older, cognitively at-risk sample, undergoing a pre-surgical evalua- tion for DBS. To the best of our knowledge, this is the first study to examine the WMT in a presumed motivated group of patients at risk for cognitive decline. Three (10%) participant’s performance fell within “fail” range group on the WMT. Although this should be interpreted with caution given our small sample size and the fact that these failures may have stemmed from individual dif- ferences, it is noteworthy that their average performance on neuropsychological tests was grossly intact. This may suggest that although their engagement levels were below expectation on the WMT, they were able to put forth adequate effort during testing. It is also possible that they have mild memory and/or cognitive impairments and this was reflected on the WMT per- formance. Although false positives on the WMT have been reported to be rare in populations with mild TBI (Green, Flaro & Courtney, 2009), false positives on the WMT and similar PVTs (e.g., MSVT) have been reported in dementia samples but, overall, this has received relatively less attention in populations with neurodegenerative disorder. Studies supporting the use of WMT in samples with dementia have tended to focus on the specificity of GMIP, as performance below recommended cut Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 512 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 Table 3. Mean and standard deviations of neuropsychological tests Test Group Pass (N = 16) Caution (N = 11) Fail (N = 3) MMSE 27.1 (2.3) 28.5 (2.9) 26.7 (1.2) BDI 8.4 (6.8) 12.4 (8.5) 8.6 (4.0) Attention & processing speed — Digit Span (SS) 9.6 (3.1) 11.6 (4.1) 7.3 (1.5) SDMT (z) — Written −1.0 (1.9) −1.4 (0.5) −0.7 (0.0) Oral −0.7 (0.9) −1.1 (0.6) −0.6 (0.7) TMT A (T) 45.7 (10.5) 40.5 (11.01) 46.7 (11.2) Language Animals (T) 47.5 (11.4) 48.1 (7.6) 43.7 (7.6) BNT (T) 54.3 (11.6) 56.4 (10.9) 53.4 (9.5) Memory — RAVLT (z) — Total −0.2 (1.6) −0.4 (0.5) −1.4 (0.5) Immediate Recall 0.0 (1.2) −0.5 (0.8) −0.5 (0.6) Delayed Recall −0.1 (1.3) −0.6 (0.5) −1.0 (0.7) HVLT-R (T) — Total 37.8 (5.8) 42.0 (–) — Delayed Recall 30.0 (9.2) 36.0 (–) — Recognition 38.9 (11.1) 42.0 (–) — WMS-IV LM (SS) — Immediate Recall 8.7 (3.1) 9.2 (1.3) 8.3 (2.5) Delayed Recall 8.7 (3.2) 9.5 (2.4) 7.7 (4.0) BVMT-R (T) — Total 47.1 (13.9) 41.5 (10.4) 37.7 (5.9) Delayed 48.4 (14.4) 46.0 (12.4) 41.0 (11.5) Executive function — TMT B (T) 40.9 (11.0) 42.2 (11.6) 40.3 (11.0) FAS (T) 41.7 (7.5) 40 (9.8) 38.6 (7.6) Note:IR = Mini Mental Status Examination (MMSE), Beck Depression Inventor-II (BDI-II), Symbol Digit Modality Test (SDMT), Trail Making Test A (TMT-A), Boston Naming Test (BNT), Rey Auditory Verbal Learning Test (RAVLT), Hopkins Verbal Learning Test-Revised (HVLT-R), Wechsler Memory Scale-IV (WMS-IV) Logical Memory, Brief Visuospatial Memory Test-Revised (BVMT-R), Trail Making Test B (TMT-B). scores is not uncommon. Axelrod and Schutte (2010) highlighted the weakness of the MSVT in distinguishing between a dementia group and an invalid performance group and suggested a lower cut score of 70% for the easy subtests in order to im- prove accurate detection in this population. Applying the proposed cut-score of 70% to the sample in our current study would result in a 100% pass rate, considering that in our small sample, the lowest score on subtest was 82.5%. Embedded measures of performance validity were also examined as secondary analyses, however, results did not provide any additional information, particularly for the participants that had failed the WMT. As previously stated, one participant that failed the WMT did not fail any of the embedded measures. One participant failed the RDS and RAVLT effort equation, and another one only failed the RAVLT equation. Of note, seven participants of the “pass” group also failed the RAVLT effort equation, though these were likely false positive. This finding highlights the importance of using appropriate measures when assessing for performance validity. Normative sample characteristics of some embedded PVTs may not be appropriate. For example, the normative samples used to develop the RAVLT effort equation was younger and mainly comprised of pa- tients with head injury and psychiatric conditions (Boone et al., 2005). Furthermore, other embedded measures, such as the ones derived from fluency tests, may also not be appropriate given our sample characteristics. One of the core features of PD is bradykinesia, which usually affects timed tasks such as verbal fluency, making any embedded test of performance validity derived from such tests inappropriate and biased. Embedded measures that have been studied in samples with neurodegenera- tive conditions such as the RDS and TMT B:A ratio, would be more appropriate. Although, other clinical factors (e.g., rigidity and akinesia) need to be taken into account for tests that rely on motor skills (i.e., TMT). The “caution” group had the most elevated depression scores, although this finding was not statistically significant. This group also had the lowest scores (mildly impaired) on a measures of processing speed. Previous studies have investigated the effect of depression on PVTs with the Test of Memory Malingering (TOMM) and found that failure scores were not attributed to affective state in a sample of community-dwelling older adults (Ashendorf, Constantinou, & McCaffrey, 2004). The Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 513 neurobiological basis of PD should also be considered when working with a movement disorders sample. Specifically, meso- limbic dopamine depletion observed in PD has been linked to apathy, one of the most common behavioral symptoms in PD. A recent study revealed improved apathy scores when participants with PD were treated with a selective D2/D3 receptor ago- nist (Thobois et al. 2013). Apathy, and in turn, reduced motivation, could contribute to the invalid performance observed in a small subset of the current sample. Future studies should account for apathy levels for patients with PD as well as the poten- tial for neurological diseases with varied substrates resulting in disparate diagnostic accuracies on PVTs. This pilot study has several limitations. Given the nature of the VA population, the majority of the participants were men, with women being underrepresented in the sample. Furthermore, the subgroups of interest (no diagnoses, MCI, dementia) were not equal in the number of participants. Future studies will aim to include equal and larger numbers of participants to increase power and perform parametric statistical analyses. A larger study with broader generalizability is needed to further evaluate the performance validity testing in presumably highly motivated older populations. Inclusion of additional neurocog- nitive comparison groups, such as Alzheimer’s disease, would also broaden the generalizability of these findings. Even with these limitations, this is the first study to show that individuals with a neurodegenerative disease at risk for cognitive decline are able to pass performance validity testing if motivated to do well. This pilot study is presented as a proof of concept to fur- ther the discussion regarding the complicated role of PVTs in neurodegenerative processes and the consideration of samples with presumed intrinsic motivations to perform well on neuropsychological testing. 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Performance Validity in Deep Brain Stimulation Candidates

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Oxford University Press
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10.1093/arclin/acx081
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Abstract

Objective: Effort and motivation are important factors that influence performance on neuropsychological tests. Performance validity tests (PVT) have not been investigated in a sample of individuals who are at risk for cognitive decline and are presumably highly motivated to do well. The aim of the current study is to investigate performance validity in individuals with Parkinson’s disease and essential tremor who are being considered for deep brain stimulation (DBS) surgery. Methods: Thirty DBS surgical candidates underwent neuropsychological evaluation including completion of the Word Memory Test (WMT) as well as embedded PVTs. Results: Sixteen DBS candidates (53.3%) obtained a passing WMT score, 11 patients (36.6%) obtained scores in the “caution” range, and three patients (10%) produced failing scores. None of the patients scored below an 82.5% on the first three WMT subtests. Conclusions: This pilot study is the first to describe PVT in DBS candidates and in a presumed highly motivated, older, and cognitively at-risk sample. Keywords: Dementia; Movement disorders; Elderly; Performance validity testing; Parkinson’s disease Introduction An individual’s engagement during testing can be influenced by a wide range of external and internal factors. Insufficient effort or invalid performance, specifically, has been strongly related to neuropsychological test results (Green, 2007). For this reason, the American Academy of Clinical Neuropsychology (AACN) and the National Academy of Neuropsychology (NAN) recommend to objectively measure non-credible performance through stand-alone and embedded performance validity tests (PVTs) during all neuropsychological evaluations (Bush et al., 2005; Heilbronner et al. 2009). Performance on both PVTs and cognitive measures are not only affected by intrinsic motivational factors to perform a certain way, but may also be influenced by cognitive dysfunction as observed in individuals with neurodegenerative disease (Green, Montijo, & Brockhaus, 2011). While performance validity studies have been applied to a wide range of samples considered at risk for invalid perfor- mance, only a few studies have assessed performance validity in “motivated” samples. Flaro, Green, and Robertson (2007) examined three different groups of individuals: mild to moderate traumatic brain injury (TBI) claimants with external incen- tives to perform poorly for financial compensation, individuals with a strong incentive to perform well who were going through custody battles, and a group of individuals with little to no incentive to do poorly or well (i.e., children with impairment from various medical conditions). The study used the Word Memory Test (WMT), one of the most widely used PVTs (Hartman, 2002). Results from this study demonstrated that the mild TBI claimant group failed the WMT at a higher rate than the motivated and neutral groups. Importantly, the passing rate of parents seeking custody of their children (moti- vated group) was 98.3% versus only 60% in the mild TBI group. In a similar and more recent study by Green and Flaro © Published by Oxford University Press 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US. doi:10.1093/arclin/acx081 Advance Access publication on 18 September 2017 Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 509 (2015), the authors found that adults with intellectual deficits who were involved with custody battles and hence motivated to do well, did not fail PVTs any more often than adults of higher intelligence. The comparison group of adults with intellectual deficits who had an external reason to perform poorly scored significantly lower on these tests. Similarly, Chafetz, Prentkowski, and Rao (2011) examined intrinsic motivation by comparing PVTs among three low functioning groups: social security claimants, rehabilitation service claimants who are seeking to work, and parents who are seeking reunification with their children from the Department of Family and Child Services. Results showed that all the parents seeking reunification with their children passed the PVTs. The highest failure rate was found for the social security claimants. Overall, these studies highlight the affect of intrinsic motivation to do well on PVTs in a variety of populations. It is also important to note that diseases associated with aging or other neurological illness may negatively influence PVTs. Dean, Victor, Boone, Philpott, and Hess (2009) examined performance validity indices derived from multiple tests (e.g., WAIS-III/WAIS-R Digit Span and Vocabulary, Dot Counting Test, Warrington Recognition Memory Test-Words, WMS-III Logical Memory) in a heterogeneous dementia sample and reported test specificities falling within the range of 30%–70%. Another study examined the specificity of the WAIS-IV Digit Span derived embedded validity measures (i.e., Reliable Digit Span) in a homogenous dementia sample of patients with probable Alzheimer’s disease, revealing high false positive rates and bringing into question the utility of set cut-offs with individuals exhibiting moderate to severe memory impairment (Kiewel, Wisdom, Bradshaw, Pastorek, & Strutt, 2012). The research regarding specificity of more widely used stand-alone PVTs, such as the WMT and the Medical Symptom Validity Test (MSVT), have demonstrated variable findings. For example, in a sample of 63 older patients examined in a memory disorders clinic, 42% performed below recommended threshold scores on the MSVT (Howe, Anderson, Kaufman, Sachs, & Loring, 2007). However, when considering the “genuine memory impairment profile” (GMIP), a specificity of greater than 90% was obtained (Howe & Loring, 2009). Similarly, Green and colleagues (2011) reported the WMT GMIP to have a very high specificity rate of 98.4% in possible MCI and probable dementia. Overall, the literature has focused on specificity rates of PVTs in dementia samples but it has not considered the influence of intrinsic motivation to perform well on these measures. In the current study, we conceptualized a group of patients with Parkinson’s disease (PD) and essential tremor (ET) that were being evaluated for deep brain stimulation surgery (DBS) as a group that has an intrinsic motivation to perform well. Neuropsychological assessments are routinely conducted as part of comprehensive evaluations for candidacy for DBS with good cognitive performance further endorsing a patient’s candidacy and dementia serving as a contraindication for the sur- gery. Therefore, it may be assumed that these patients wanting to undergo surgery to alleviate their symptoms are motivated to do well on neuropsychological measures, resulting in low failure rates on PVTs. This study will investigate performance validity, assessed via the WMT, in PD and ET DBS surgery candidates, who are at increased risk for cognitive impairment and who are presumably intrinsically motivated to perform well. Methods Participants Thirty DBS candidates (28 men; two women) from the Neurology departments of the Michael E. DeBakey VA Medical Center and Baylor College of Medicine underwent neuropsychological evaluations including completion of the Word Memory Test (WMT). The observed male predominance of the sample was expected given that only 10% of the Veteran pop- ulation are women. The sample consisted of 20 participants with PD and 10 with ET (M = 65.9, SD = 8.3; range = age age 48–90). The average years of education of the sample was 13.2 (SD = 2.3; range = 8–18). Diagnostically, 15 participants did not meet criteria for a neurocognitive disorder, while two participants were diagnosed with PD-Dementia, and 13 were diag- nosed with PD-Mild Cognitive Impairment (PD-MCI). Of those, three individuals met criteria for amnestic PD-MCI and 10 patients met criteria for non-amnestic PD-MCI. For patients with PD, the median Hoehn and Yahr disease stage was 2.5 (range = 0–5). Based on the Unified Parkinson’s Disease Rating Scale (UPDRS), the mean motor score for participants with PD was 22.5 (SD = 14.3). Only six participants with essential tremor had motor data available from the Essential Tremor Rating Assessment Scale (TETRAS; M = 30.9, SD = 2.0). Procedures The Word Memory Test was administered to patients at the beginning of the neuropsychological evaluation. For any fail- ing scores on the easy subtests (IR, Immediate Recognition; DR, Delayed Recognition; CN, Consistency), the GMIP was cal- culated based on the average difference between easy and hard WMT subtests (MC, Multiple Choice; PA, Paired Associates; Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 510 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 FR, Free Recall) (Green, Lees-Haley, & Allen, 2003). Given the clinical nature of the assessment, there was some variability in measures completed by the patients. The assessment included the following measures: Mini Mental Status Examination (MMSE; n = 30), Beck Depression Inventory-II (BDI-II; n = 30), Wechsler Adult Intelligence Scale-IV (WAIS-IV) Digit Span (n = 28), Rey Auditory Verbal Learning Test (RAVLT, n = 22), Hopkins Verbal Learning Test-Revised (HVLT-R; n = 7), Wechsler Memory Scale-IV (WMS-IV) Logical Memory (n = 29), Brief Visuospatial Memory Test-Revised (BVMT-R; n = 29), Trail Making Test A (TMT-A; n = 30), Trail Making Test B (TMT-B; n = 30), Symbol DigitModalityTest(SDMT)Oral(n = 28) and Written (n = 26), Boston Naming Test (BNT; n = 29), Verbal Fluency (FAS; n = 29 & Animals = 28), and the Word Memory (WMT; n = 30). The BDI, SDMT, WAIS-IB DS, HVLT-R, WMS-IV LM, and BVMT-R were scored and normed with the normative data provided on their respective manuals. The Geffen, Geffen, and Bishop (1997) normativedatawas used forthe RAVLT. The Revised Comprehensive Norms for an Expanded Halstead-Reitan Battery Heaton norms were used to score the TMT, BNT, FAS, and Animals (Heaton, Miller, Taylor, & Grant, 2004). The following embedded measures of performance validity were also examined: reliable digit span (RDS) with a cut score <6(Kiewel et al., 2012); Animals and FAS verbal fluency T-scores with cut scores of <33 and <30, respectively (Sugarman & Axelrod, 2015); ratio of TMT B:A with a cut-score of <1.50 (Iverson, Lange, Green, & Franzen, 2002); RAVLT recognition combination equation with a cut-score of <12 (Boone, Lu, & Wen, 2005); BVMT-R retention percentage with a cut-score of <58% (Sawyer, Testa, & Dux, 2017); and the HVLT-R Recognition Discrimination Index of a cut-score of <5(Sawyer et al., 2017). Results Participant’s scores can be found in Table 1. Using standardized cut scores (Green, 2005), 90% of the patients passed the WMT based on their scores on the easy subtests. Specifically, a total of 16 DBS candidates obtained a WMT “pass” score (>90%), whereas 11 patients obtained scores in the “caution” range (scores between 83% and 90%, considered passing), and Table 1. Word Memory Test Performance Movement disorder Cognitive diagnosis Age Edu. IR DR CN MC PA FR ET None 48.0 15.0 100.0 100.0 100.0 100.0 100.0 55.0 ET None 90.0 11.0 100.0 97.5 97.5 90.0 90.0 17.5 ET MCI-EF 56.0 13.0 100.0 92.5 92.5 60.0 65.0 45.0 ET** MCI-PS&EF 64.0 12.0 100.0 87.5 87.5 75.0 65.0 32.5 ET* None 74.0 12.0 100.0 82.5 82.5 80.0 65.0 25.0 ET None 75.0 11.0 97.5 92.5 95.0 70.0 80.0 35.0 ET** None 69.0 12.0 95.0 90.0 90.0 70.0 70.0 35.0 ET** MCI-EF 67.0 12.0 92.5 95.0 87.5 55.0 50.0 35.0 ET** None 66.0 14.0 92.5 90.0 87.5 55.0 60.0 35.0 ET* MCI-EF 67.0 13.0 87.5 95.0 82.5 35.0 40.0 17.5 PD None 62.0 16.0 100.0 100.0 100.0 100.0 100.0 55.0 PD None 59.0 16.0 100.0 97.5 97.5 100.0 95.0 67.5 PD PD-Dementia 71.0 14.0 100.0 97.5 97.5 100.0 75.0 35.0 PD MCI-Amnestic 69.0 11.0 100 97.5 97.5 75.0 65.0 37.5 PD None 61.0 10.0 100 95.0 95.0 90.0 85.0 35.0 PD MCI-Amnestic 69.0 16.0 97.5 100.0 97.5 95.0 85.0 55.0 PD None 64.0 18.0 97.5 95.0 97.5 75.0 65.0 32.5 PD** MCI-EF 67.0 16.0 97.5 92.5 90.0 100.0 95.0 45.0 PD** MCI-EF 64.0 12.0 97.5 90.0 87.5 60.0 70.0 37.5 PD* MCI-Amnestic 67.0 16.0 97.5 82.5 85.0 80.0 80.0 45.0 PD None 57.0 12.0 95.0 100.0 95.0 100.0 95.0 47.5 PD None 61.0 12.0 95.0 100.0 95.0 100.0 90.0 77.5 PD MCI-EF 66.0 12.0 95.0 97.5 97.5 70.0 70.0 55.0 PD MCI-multi-domain 48.0 12.0 95.0 95.0 95.0 85.0 75.0 37.5 PD None 78.0 8.0 95.0 95.0 95.0 45.0 40.0 37.5 PD** None 67.0 16.0 92.5 97.5 90.0 75.0 80.0 47.5 PD** PD-Dementia 69.0 12.0 92.5 87.5 90.0 50.0 40.0 22.5 PD** MCI-EF 74.0 14.0 87.5 92.5 85.0 80.0 65.0 42.5 PD** MCI-EF 61.0 12.0 85.0 97.5 87.5 75.0 65.0 25.0 PD** None 66.0 16.0 85.0 90.0 85.0 60.0 60.0 32.5 Note:PD = Parkinson’s disease; ET = essential tremor; MCI = mild cognitive impairment; EF = executive function; IR = immediate recall; D = delayed recall; CN = consistency; MC = multiple choice; PA = paired associates; FR = free recall; PS = processing speed.*Fail Score (bold); **Caution Score (italic). Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 511 Table 2. Frequency of patients who failed embedded measures of performance validity WMT test results Embedded measures Pass Caution Fail RDS (<6) 0 0 1 BVMT PR (<58%) 0 1 0 RAVLT EE (<12) 7 7 1 HVLT-R RDI (<5) 1 0 0 TMT B:A Ratio (<1.50) 0 1 0 FAS (T < 30) 0 1 0 Animals (T < 33) 0 1 0 Note: RDS = Reliable Digit Span; BVMT PR = Brief Visual Memory Test Percent Retention; RAVLT EE = Rey Auditory Verbal Learning Test Effort Equation; HVLT-R RDI = Hopkins Verbal Learning Test-Revised Recognition Discrimination Index; TMT B:A = Trail Making Test Ratio of B:A; WMT = Word Memory Test. three patients produced failing scores (<82.5%). Two of the three WMT failures met the 30 point GMIP criteria. Of these pa- tients, one had a diagnosis of PD-MCI, and one did not meet criteria for a neurocognitive disorder. Computing classification accuracy based on embedded PVTs was not appropriate considering the small sample size of the study; therefore, the results of these measures were only qualitatively examined. The frequencies of pass and failures of all embedded PVTs examined can be found in Table 2. Broadly, there was no clear pattern with the embedded performance validity measures and participants appeared equally likely to fail an embedded PVT as opposed to the WMT. However, it was noteworthy that 50% of the sample failed the RAVLT effort equation. The three participants that scored in the failure range of the WMT had variable performance on the embedded measures. One of the participants, who was not diagnosed with a cognitive disorder, scored below cut scores only on the RDS and the RAVLT equation. The second participant in this cate- gory, who was diagnosed with amnestic MCI, scored below expectation only on the RAVLT embedded measure. Lastly, the third participant who diagnosed with MCI-non-amnestic, did not score below cut scores on any embedded PVTs. Statistical analyses of the neuropsychological data were not appropriate given the small sample size of this pilot study (Table 3). Nevertheless, qualitative observations about the average scores can be made regarding the performance of each group. Performance on measures of brief attention, visual scanning, executive function, language, contextual verbal memory, and visual memory was low average to average across the three groups. Depression scores were highest for the “caution” group. On a measure of written processing speed, the “caution” group performed in the mildly impaired range compared to average performances in the other groups. There were three participants who scored 82.5 (DR & CN; see Table 1), which is considered the highest threshold for a failure and no participants scored below 82.5. v Discussion This proof of concept study examined PVTs in a sample of motivated pre-surgical DBS candidates who are experiencing cognitive decline or are at risk of future decline given their neurodegenerative diagnoses. Although half of the participants were diagnosed with a neurocognitive disorder, it is presumed they were motivated to have the surgery and improve their quality of life, resulting in intrinsic motivation to perform well on the WMT and cognitive assessment. Previous research investigating the use of PVTs in dementia and mild cognitive impairment samples resulted in conflicting results (Green et al., 2011; Walter, Morris, Swier-Vosnos, & Pliskin, 2014). However, this study demonstrates high passing rates (90%) of a stand-alone PVT in a presumed highly motivated older, cognitively at-risk sample, undergoing a pre-surgical evalua- tion for DBS. To the best of our knowledge, this is the first study to examine the WMT in a presumed motivated group of patients at risk for cognitive decline. Three (10%) participant’s performance fell within “fail” range group on the WMT. Although this should be interpreted with caution given our small sample size and the fact that these failures may have stemmed from individual dif- ferences, it is noteworthy that their average performance on neuropsychological tests was grossly intact. This may suggest that although their engagement levels were below expectation on the WMT, they were able to put forth adequate effort during testing. It is also possible that they have mild memory and/or cognitive impairments and this was reflected on the WMT per- formance. Although false positives on the WMT have been reported to be rare in populations with mild TBI (Green, Flaro & Courtney, 2009), false positives on the WMT and similar PVTs (e.g., MSVT) have been reported in dementia samples but, overall, this has received relatively less attention in populations with neurodegenerative disorder. Studies supporting the use of WMT in samples with dementia have tended to focus on the specificity of GMIP, as performance below recommended cut Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 512 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 Table 3. Mean and standard deviations of neuropsychological tests Test Group Pass (N = 16) Caution (N = 11) Fail (N = 3) MMSE 27.1 (2.3) 28.5 (2.9) 26.7 (1.2) BDI 8.4 (6.8) 12.4 (8.5) 8.6 (4.0) Attention & processing speed — Digit Span (SS) 9.6 (3.1) 11.6 (4.1) 7.3 (1.5) SDMT (z) — Written −1.0 (1.9) −1.4 (0.5) −0.7 (0.0) Oral −0.7 (0.9) −1.1 (0.6) −0.6 (0.7) TMT A (T) 45.7 (10.5) 40.5 (11.01) 46.7 (11.2) Language Animals (T) 47.5 (11.4) 48.1 (7.6) 43.7 (7.6) BNT (T) 54.3 (11.6) 56.4 (10.9) 53.4 (9.5) Memory — RAVLT (z) — Total −0.2 (1.6) −0.4 (0.5) −1.4 (0.5) Immediate Recall 0.0 (1.2) −0.5 (0.8) −0.5 (0.6) Delayed Recall −0.1 (1.3) −0.6 (0.5) −1.0 (0.7) HVLT-R (T) — Total 37.8 (5.8) 42.0 (–) — Delayed Recall 30.0 (9.2) 36.0 (–) — Recognition 38.9 (11.1) 42.0 (–) — WMS-IV LM (SS) — Immediate Recall 8.7 (3.1) 9.2 (1.3) 8.3 (2.5) Delayed Recall 8.7 (3.2) 9.5 (2.4) 7.7 (4.0) BVMT-R (T) — Total 47.1 (13.9) 41.5 (10.4) 37.7 (5.9) Delayed 48.4 (14.4) 46.0 (12.4) 41.0 (11.5) Executive function — TMT B (T) 40.9 (11.0) 42.2 (11.6) 40.3 (11.0) FAS (T) 41.7 (7.5) 40 (9.8) 38.6 (7.6) Note:IR = Mini Mental Status Examination (MMSE), Beck Depression Inventor-II (BDI-II), Symbol Digit Modality Test (SDMT), Trail Making Test A (TMT-A), Boston Naming Test (BNT), Rey Auditory Verbal Learning Test (RAVLT), Hopkins Verbal Learning Test-Revised (HVLT-R), Wechsler Memory Scale-IV (WMS-IV) Logical Memory, Brief Visuospatial Memory Test-Revised (BVMT-R), Trail Making Test B (TMT-B). scores is not uncommon. Axelrod and Schutte (2010) highlighted the weakness of the MSVT in distinguishing between a dementia group and an invalid performance group and suggested a lower cut score of 70% for the easy subtests in order to im- prove accurate detection in this population. Applying the proposed cut-score of 70% to the sample in our current study would result in a 100% pass rate, considering that in our small sample, the lowest score on subtest was 82.5%. Embedded measures of performance validity were also examined as secondary analyses, however, results did not provide any additional information, particularly for the participants that had failed the WMT. As previously stated, one participant that failed the WMT did not fail any of the embedded measures. One participant failed the RDS and RAVLT effort equation, and another one only failed the RAVLT equation. Of note, seven participants of the “pass” group also failed the RAVLT effort equation, though these were likely false positive. This finding highlights the importance of using appropriate measures when assessing for performance validity. Normative sample characteristics of some embedded PVTs may not be appropriate. For example, the normative samples used to develop the RAVLT effort equation was younger and mainly comprised of pa- tients with head injury and psychiatric conditions (Boone et al., 2005). Furthermore, other embedded measures, such as the ones derived from fluency tests, may also not be appropriate given our sample characteristics. One of the core features of PD is bradykinesia, which usually affects timed tasks such as verbal fluency, making any embedded test of performance validity derived from such tests inappropriate and biased. Embedded measures that have been studied in samples with neurodegenera- tive conditions such as the RDS and TMT B:A ratio, would be more appropriate. Although, other clinical factors (e.g., rigidity and akinesia) need to be taken into account for tests that rely on motor skills (i.e., TMT). The “caution” group had the most elevated depression scores, although this finding was not statistically significant. This group also had the lowest scores (mildly impaired) on a measures of processing speed. Previous studies have investigated the effect of depression on PVTs with the Test of Memory Malingering (TOMM) and found that failure scores were not attributed to affective state in a sample of community-dwelling older adults (Ashendorf, Constantinou, & McCaffrey, 2004). The Downloaded from https://academic.oup.com/acn/article/33/4/508/4161105 by DeepDyve user on 13 July 2022 M.A. Rossetti et al. / Archives of Clinical Neuropsychology 33 (2018); 508–514 513 neurobiological basis of PD should also be considered when working with a movement disorders sample. Specifically, meso- limbic dopamine depletion observed in PD has been linked to apathy, one of the most common behavioral symptoms in PD. A recent study revealed improved apathy scores when participants with PD were treated with a selective D2/D3 receptor ago- nist (Thobois et al. 2013). Apathy, and in turn, reduced motivation, could contribute to the invalid performance observed in a small subset of the current sample. Future studies should account for apathy levels for patients with PD as well as the poten- tial for neurological diseases with varied substrates resulting in disparate diagnostic accuracies on PVTs. This pilot study has several limitations. Given the nature of the VA population, the majority of the participants were men, with women being underrepresented in the sample. Furthermore, the subgroups of interest (no diagnoses, MCI, dementia) were not equal in the number of participants. Future studies will aim to include equal and larger numbers of participants to increase power and perform parametric statistical analyses. A larger study with broader generalizability is needed to further evaluate the performance validity testing in presumably highly motivated older populations. Inclusion of additional neurocog- nitive comparison groups, such as Alzheimer’s disease, would also broaden the generalizability of these findings. Even with these limitations, this is the first study to show that individuals with a neurodegenerative disease at risk for cognitive decline are able to pass performance validity testing if motivated to do well. This pilot study is presented as a proof of concept to fur- ther the discussion regarding the complicated role of PVTs in neurodegenerative processes and the consideration of samples with presumed intrinsic motivations to perform well on neuropsychological testing. 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Journal

Archives of Clinical Neuropsychology – Oxford University Press

Published: Jun 1, 2018

Keywords: dementia; essential tremor; movement disorders; memory; deep brain stimulation

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