Performance and symptom validity assessment in attention deficit/hyperactivity disorder: Base rates of invalidity, concordance, and relative impact on cognitive performance.

Objective: Differential diagnosis of attention deficit/hyperactivity disorder (ADHD) is one of the most common referral questions for neuropsychological evaluation but is complicated by the presence of external incentives. Validity assessment is therefore critical in such evaluations, employing symptom validity tests (SVTs) and performance validity tests (PVTs) to assess the validity of reported symptoms and cognitive test performance, respectively. This study aimed to establish the base rate of symptom and performance invalidity in adults referred for ADHD, compare concordance between performance and symptom validity, and assess the impact of each type of validity on cognitive test performance. Method: This consecutive case series included data from 392 demographically-diverse adults who underwent outpatient neuropsychological evaluation for ADHD. All patients were administered the Clinical Assessment of Attention Deficit-Adult (CAT-A) and a uniform cognitive test battery, including seven PVTs. Results: Invalid symptom reporting and PVT performance were found in 22% and 16% of the sample, respectively. Sixty-eight percent had concordantly valid SVTs/PVTs and 6% had invalid SVTs/PVTs, whereas the remaining 26% had either invalid SVTs or PVTs (but not both). Invalid PVT performance resulted in a significant decrease across all cognitive test scores, with generally large effects (ηp2=.01-.18). Invalid symptom reporting had minimal effects on cognitive test performance (ηp2= ≤.04). Conclusions: PVTs and SVTs are dissociable and therefore should not be used interchangeably in the context of adult ADHD evaluations. Rather, symptom and performance validity should continue to be assessed independently as they provide largely non-redundant information.

Assessing performance validity during attention-deficit/hyperactivity disorder evaluations: Cross-validation of non-memory embedded validity indicators.

Embedded performance validity tests (PVTs) are key components of neuropsychological evaluations. However, most are memory-based and may be less useful in the assessment of attention-deficit/hyperactivity disorder (ADHD). Four non-memory-based validity indices derived from processing speed and executive functioning measures commonly included in ADHD evaluations, namely Verbal Fluency (VF) and the Trail Making Test (TMT), were cross-validated using the Rey 15-Item Test (RFIT) Recall and Recall/Recognition as memory-based comparison measures. This consecutive case series included data from 416 demographically-diverse adults who underwent outpatient neuropsychological evaluation for ADHD. Validity classifications were established, with ≤1 PVT failure of five independent criterion PVTs as indicative of valid performance (374 valid performers/42 invalid performers). Among the statistically significant validity indicators, TMT-A and TMT-B T-scores (AUCs = .707-.723) had acceptable classification accuracy ranges and sensitivities ranging from 29%-36% (≥89% specificity). RFIT Recall/Recognition produced similar results as TMT-B T-score with 42% sensitivity/90% specificity, but with lower classification accuracy. In evaluating adult ADHD, VF and TMT embedded PVTs demonstrated comparable sensitivity and specificity values to those found in other clinical populations but necessitated alternate cut-scores. Results also support use of RFIT Recall/Recognition over the standard RFIT Recall as a PVT for adult ADHD evaluations.