Excessive decline from premorbid functioning: detecting performance invalidity with the WAIS-IV and demographic predictions

Objective: Excessive Decline from Premorbid Functioning (EDPF) is presented as a construct and defined as a discrepancy between predicted premorbid ability and current test performance that is so atypical of individuals with true neurocognitive impairment that it is likely the product of performance invalidity. New embedded PVTs (EDPF-FSIQ, EDPF-VW, and EDPF-PP) were derived by comparing scores from the WAIS-IV to TOPF demographically predicted premorbid estimates and then examined for classification accuracy.

Participants and methods: After excluding for dementia, intellectual disability, and left-sided stroke, participants (n = 230) were grouped according to number of PVTs failed. ROC analyses were conducted to determine the accuracy of EDPF indices in classifying patients as failing 0 or ≥2 PVTs within both a mixed neuropsychological outpatient sample and according to specific diagnostic criterion groups.

Results: Significant group differences emerged for all EDPF indices (p < .001). EDPF-FSIQ resulted in an AUC of .837, classifying patients with 56% sensitivity at ≥90% specificity, and EDPF-VW resulted in an AUC of .850, classifying patients with 61% sensitivity at ≥90% specificity. Accuracy remained high across diagnostic groups (i.e. neurocognitive, moderate/severe TBI, and psychiatric) for EDPF-VW and EDPF-FSIQ, whereas specificity declined for EDPF-PP in patients with mixed neurocognitive disorders. Overall, classification accuracy rates exceeded those of Reliable Digit Span.

Conclusions: Both EDPF-FSIQ and EDPF-VW demonstrated excellent discrimination between patients providing valid versus invalid test performance. Unique advantages of EDPF validity measures include incorporation of demographic estimates of premorbid ability and examination of performances on multiple tests spanning different cognitive domains.