Neuropsychological Performance Validity in New Zealand’s Accident Compensation Corporation Assessments of TBI

Abstract

Evidence from various populations suggests that symptom complaints and effort applied in test performance during neuropsychological assessment are not always genuine. Despite the recognised importance of validity in neuropsychological assessment, at present there are only two published papers on the assessment of performance validity (PV) in New Zealand. New Zealand's system for managing personal injury is systemically different to international contexts, being managed by the Accident Compensation Corporation, a crown organisation which provides comprehensive, no-fault personal injury cover for all New Zealand residents and visitors. Specifically unlike international contexts, it provides compensation and support following a personal injury and precludes litigation for damages. This research project aimed to expand on this by exploring those factors associated with; (1) results of embedded and external measures of performance validity (PV-TI), and (2) conclusions drawn by clinicians about performance validity (PV-CC). It also examined those factors associated with discrepancies between test indicators and clinical conclusions. Finally, the project explored those actions or recommendations provided by clinicians working in the ACC when PV concerns were identified. A file audit was conducted on 219 neuropsychological reports from ACC and statistical analyses were conducted. This study found that PV was assessed in 94% of cases, with no performance validity concerns were identified in 72% of tests, and clinicians concluding that there were no performance validity concerns in 79% cases. Those factors that were associated with clinician conclusions and test indicators of performance validity were evaluated using Analysis of Variance (for continuous variables) and chi-square analysis (for categorical variables). Factors associated with both PV-TI and PV-CC were clinician gender (males), and shorter length of PTA. Additional factors associated only with PV-TI were client age (being older), and clinician qualification (doctorally qualified candidates more likely to have test findings indicating PV). Of all factors evaluated, two were significantly associated with a discrepancy between test indicators and clinical conclusions; no loss of consciousness and increased client age. This indicates that these may be factors that clinicians are using to contextualize test indicators of PV in making clinical judgments. The most common recommendation following a finding of PV was psychiatric referral. Of note, unlike studies conducted both internationally and in New Zealand factors including ethnicity and place of birth, prior forensic, pre-and-post injury mental health complaint, and being compensation seeking were not significantly associated with performance invalidity (clinician conclusion, or test result)in this sample. These results and their limitations are discussed with conclusions drawn being of relevance to those working in adult neuropsychology in New Zealand.