Abstract
A decade of research has both illustrated the need for accurate clinical assessment of adult ADHD and brought forward a series of validity indicators assisting this diagnostic process. Several of these indicators have been embedded into Conners’ Adult ADHD Rating Scales (CAARS). As their different theoretical underpinnings offer the opportunity of possible synergy effects, the present study sought to examine whether the item- or index-wise combination of multiple validity indicators benefits classification accuracy. A sample of controls (n = 856) and adults with ADHD (n = 72) answered the CAARS, including the ADHD Credibility Index (ACI) honestly, while a group of instructed simulators (n = 135) completed the instrument as though they had ADHD. First, original CAARS items, which are part of the CAARS Infrequency Index (CII), and items drawn from the ACI were combined into a new CII-ACI-Compound Index. Secondly, existing validity indicators, including suspect T-score elevations and the CII, were considered in combination. Both approaches were evaluated in terms of sensitivity and specificity. The combination of four CII and five ACI items into the CII-ACI-Compound Index yielded a sensitivity between 41 and 51% and an estimated specificity above 87%. Suspect T-score elevations on all three DSM scales emerged as another potentially useful validity indicator with a sensitivity of 45 to 46% and a specificity > 90%. Deeming examinees non-credible whenever two or more validity indicators showed suspect results ensured low false-positive rates (< 10%), but reduced sensitivity significantly. Classifying respondents as non-credible as soon as any given indicator fell into the suspect range resulted in frequent false positives (> 11% of misclassified adults with ADHD). Depending on whether high specificity or high sensitivity is prioritized, such combined considerations offer valuable additions to individual validity indicators. High sensitivity provided by “either/or” combinations could prove useful in screening settings, whereas high stakes settings could benefit from “and” combinations.
Highlights
There is a high need for efficient validity indicators in the clinical assessment of adult ADHD, as an ever-growing evidence base suggests that individuals motivated to feign the disorder are able to do so convincingly on a variety of instruments routinely used in clinical practice
Evidence suggesting that individuals feigning ADHD tend to over-endorse symptoms illustrates the possible use of another validity indicator described in the Conners’ Adult ADHD Rating Scales (CAARS) manual (Conners et al, 1999)
With each item being scored on a scale from 0 to 3, possible sum scores on the CAARS Infrequency Index (CII)-ACICompound Index ranged from 0 to 27
Summary
There is a high need for efficient validity indicators in the clinical assessment of adult ADHD, as an ever-growing evidence base suggests that individuals motivated to feign the disorder are able to do so convincingly on a variety of instruments routinely used in clinical practice. Respondents most commonly believed individuals with such a diagnosis to benefit from access to accommodations in the academic context, followed by prescription of stimulant medication, or advantages in social interactions (e.g., receiving attention, having an excuse for occasional misconduct) These numbers appear to translate into high base rates of feigned ADHD, among university students. In 2011, Suhr and colleagues introduced the first embedded validity indicator aiding the detection of feigned ADHD, which is based on infrequent as opposed to inconsistent symptom reports Their CAARS Infrequency Index (CII) includes original CAARS items which are rarely endorsed by genuine patients with ADHD and neurotypical controls (see “Method” for additional details). Cross-validations of the CII revealed variable, but promising classification accuracy (Cook et al, 2016, 2017; Edmundson et al, 2017; Fuermaier et al, 2016a, b; Harrison & Armstrong, 2016; Walls et al, 2017)
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