Symptom validity testing in adults with clinically diagnosed ADHD: comparison of the Conner's Adult ADHD Rating Scale...

Compared to the number of performance validity measures, the range of available symptom validity measures is limited. The Self-Report Symptom Inventory (SRSI) is a recently developed freestanding symptom validity test with promising psychometric characteristics for use on non-criminal forensic and a range of clinical populations. The goal of this study was to evaluate the utility of the SRSI for symptom validity testing in the clinical evaluation of adults with attention-deficit/hyperactivity disorder (ADHD).

This analogue study compared 76 German patients diagnosed with ADHD (age range 19-63 years) with typically developing individuals from the Netherlands/Germany who were assigned to either a control group (N = 58; age range 18-73 years) or a simulation group (N = 46; age range 18-57 years). All participants completed the Conners' Adult ADHD Rating Scale (CAARS) with its two embedded validity indicators Infrequency Index (CII) and ADHD Credibility Index (ACI), the SRSI, and the Digit Span (to derive the Reliable Digit Span).

Specificity in controls was perfect for the CAARS, but reached only about 90% for the SRSI. In contrast, sensitivity in experimental simulators ranged from 24% to 65% for the CAARS, but reached high rates of 69% to 82% for the SRSI. In the sample of patients with ADHD, the failure rate ranged from 8% to 34% (CAARS), and 33% to 47% (SRSI). Further, we found limited classification agreement between the validity measures.

The divergent results on the different validity indicators reflects the ongoing discussion on poor construct unity and clarity, and calls for more research addressing the heterogeneous construct. The utility of the SRSI to reliably distinguish between valid and invalid symptom report in the clinical evaluation of adult ADHD has to be investigated by more refined studies including both symptom and performance validity indicators.