The Pain Disability Index: Effects of performance and symptom validity in mild traumatic brain injury litigants with persistent Post-Concussion pain complaints

Abstract

Objective Objectives of the current study were to cross validate the Pain Disability Index (PDI) as a measure of symptom validity in a large sample of mild traumatic brain injury (MTBI) litigants with persistent post-concussive pain complaints, and investigate the effects of performance and symptom validity testing on PDI scores. Methods Participants included 91 adults who underwent a comprehensive neuropsychological examination. Criterion groups were formed based upon their performance on stand-alone measures of cognitive performance validity (PVT), and the MMPI-2-RF Symptom Validity Scale (FBS-r) as a measure of symptom validity (SVT). Results Participants who failed PVT and SVT scored significantly higher on the PDI compared to participants who passed both. Failing both was associated with a large effect size. Failing PVT, but passing SVT, was associated with a medium effect on PDI scores, while passing PVT, but failing SVT demonstrated a small effect. A PDI cutscore of 49 was associated with .90 specificity and .47 sensitivity. Conclusion The PDI demonstrates external validity as a self-report measure of symptom validity in MTBI litigants with persistent post-concussive pain complaints. A dose response relationship exists between PVT, SVT and PDI scores. Forensic examiners should include both PVT and SVT to optimize clinical decision making when evaluating MTBI litigants with complaints of pain-related disability years post-incident.