WAIS-IV GAI and CPI discrepancies in multiple sclerosis and traumatic brain injury

We examined relationships between the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) General Ability Index (GAI) and Cognitive Proficiency Index (CPI) in two clinical samples. The mean pattern produced by 42 individuals with multiple sclerosis (MS) and 47 with traumatic brain injury (TBI) was the same, GAI > CPI. This pattern occurred in 61.9% and 78.7% of the protocols of patients with MS or TBI, respectively. The MS sample earned a significantly larger CPI mean than did patients with TBI. The group means did not differ on the GAI. Patients with TBI had significantly larger GAI-CPI discrepancy score means than those with MS. Receiver operating characteristics (ROC) analysis assessed the ability of GAI-CPI discrepancies to differentiate the samples. The area under curve (AUC) was 0.67, 95% [0.55, 0.78], which indicated low accuracy in terms of group classification.