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Review of Statistical and Methodological Issues in the Forensic Prediction of Malingering from Validity Tests: Part II—Methodological Issues

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Abstract

Forensic neuropsychological examinations to detect malingering in patients with neurocognitive, physical, and psychological dysfunction have tremendous social, legal, and economic importance. Thousands of studies have been published to develop and validate methods to forensically detect malingering based largely on approximately 50 validity tests, including embedded and stand-alone performance and symptom validity tests. This is Part II of a two-part review of statistical and methodological issues in the forensic prediction of malingering based on validity tests. The Part I companion paper explored key statistical issues. Part II examines related methodological issues through conceptual analysis, statistical simulations, and reanalysis of findings from prior validity test validation studies. Methodological issues examined include the distinction between analog simulation and forensic studies, the effect of excluding too-close-to-call (TCTC) cases from analyses, the distinction between criterion-related and construct validation studies, and the application of the Revised Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2) in all Test of Memory Malingering (TOMM) validation studies published within approximately the first 20 years following its initial publication to assess risk of bias. Findings include that analog studies are commonly confused for forensic validation studies, and that construct validation studies are routinely presented as if they were criterion-reference validation studies. After accounting for the exclusion of TCTC cases, actual classification accuracy was found to be well below claimed levels. QUADAS-2 results revealed that extant TOMM validation studies all had a high risk of bias, with not a single TOMM validation study with low risk of bias. Recommendations include adoption of well-established guidelines from the biomedical diagnostics literature for good quality criterion-referenced validation studies and examination of implications for malingering determination practices. Design of future studies may hinge on the availability of an incontrovertible reference standard of the malingering status of examinees.

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Notes

  1. The term “forensic” shall refer to any situation where there is an actual or potential legal question regarding the veracity of an examinee’s presentation, such as when making decisions about the presence of sexual abuse, eligibility for disability benefits, fitness for fulfilling a particular role such as being a parent or police officer, ability to stand trial, presence of neurocognitive or psychiatric conditions that may affect guilt, innocence, or sentencing of a criminal defendant, tort situations involving questions of the veracity of neurocognitive abilities and related conditions. Such actual or potential legal questions arise most frequently in medicolegal settings, but may arise also in clinical contexts (cf. Sherman et al., 2020, p. 9; Sweet et al., 2021, p. 1059).

  2. Throughout both parts of the review, the following naming conventions are used. Presence of malingering is denoted \({M}^{+}\) and the absence of malingering is denoted \({M}^{-}\). A positive finding on a PVT indicative of \({M}^{+}\) is denoted \({PVT}^{+}\), while a negative finding on a PVT indicative of \({M}^{-}\) is denoted \({PVT}^{-}\). Note that in prior writing (e.g., Chafetz, 2011; Larrabee, 2008), the wording “failure on” or “failing” a PVT is sometimes used to denote a positive finding on a PVT \({(PVT}^{+})\). “Passing a PVT” is sometimes used to denote a negative finding on a PVT \({(PVT}^{-})\) indicative of credible responding that would not lead to a determination of malingering \({(M}^{-})\). In keeping with the terminology from the medical diagnostics literature that a positive result on a test indicates presence of the attribute tested, these papers use the term “positive finding on a PVT” (\({PVT}^{+}\)) to indicate “failing” a PVT. “Negative finding on a PVT” (\(P{VT}^{-}\)) will indicate “passing” the PVT. Symbolically, this will be denoted by \({PVT}^{+}\) and \({PVT}^{-}\). Implications of these naming conventions are discussed in more detail in Part I.

  3. A “confusion table” or “confusion matrix” is a 2 × 2 diagnostic classification table (see Figs. 1 and 2 in Part I). It is a special case of the 2 × 2 contingency table often used in psychological research to show the association of two binary variables. In a confusion table, columns reflect the criterion values (here, \({M}^{+}\) and \({M}^{-}\)), while rows reflect the predictor values (here, \({PVT}^{+}\) and \({PVT}^{-}\)).

  4. In Martin et al. (2020, their Table 5, pp. 99–100), 53 TOMM studies are listed with additional two studies listed on p. 112 for a total of 55 studies. However, there is inconsistency in how studies from articles that report multiple studies are listed in Martin et al. (2020). For consistency, in the present review, each separate study, whether reported in a publication with other studies or by itself, is counted separately. There are also two studies among the original list not discussed in this review and one not in the original list that is discussed: Instead of Ashendorf et al. (2003), Ashendorf et al. (2004) was included because the former presents no TOMM results while the latter does. It was therefore assumed Ashendorf et al. (2003) had been mistakenly cited in Martin et al. (2020). Another study (Greiffenstein et al., 2008) was excluded because, upon examination, data related to TOMM validation referenced in Martin et al. (2020, p. 99) could not be found.

  5. Notably, the call to use STARD was not repeated in the updated 2021 AACN consensus statement (Sweet et al., 2021).

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Correspondence to Christoph Leonhard.

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No parts of this work have been presented elsewhere. However, in compliance with data sharing requirements, data and analysis presented in Fig. 1, Table 4, and in the Supplemental Appendix (use of QUADAS-2 by two raters on 20 TOMM validation studies) have been publicly shared under the following Figshare https://doi.org/10.6084/m9.figshare.14368739.v1.

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Leonhard, C. Review of Statistical and Methodological Issues in the Forensic Prediction of Malingering from Validity Tests: Part II—Methodological Issues. Neuropsychol Rev 33, 604–623 (2023). https://doi.org/10.1007/s11065-023-09602-6

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