The Severe Impairment Profile: A Conceptual Shift

Abstract

Objective: The current study sought to evaluate and replicate the severe impairment profile (SIP) of the Word Memory Test (WMT) in patients referred for dementia evaluations.

Method: The sample consisted of 125 patients referred for a neuropsychological evaluation at a large Veterans Affairs Medical Center. Patients were assigned a Clinical Dementia Rating (CDR) by blind raters, and were classified according to their performance on performance validity testing. Subsequent chart reviews were conducted to help in more accurately determining the presence of severe memory impairment likely due to an underlying dementing process versus poor effort/task engagement.

Results: In our sample, 51% of patients failed easy WMT subtests and 93% of these patients obtained the SIP. The rates of failure on these easy subtests generally coincided with both more severely impaired CDR ratings, as well as more impaired delayed memory composite scores. Upon chart review, it was determined that there were likely a significant portion of classification errors using the SIP, with a positive posttest probability of impairment based on having the SIP being 65% as opposed to 28% for a negative result.

Conclusions: Our findings suggest that the SIP does not appear to function effectively in a mixed dementia sample where there is increased potential for secondary gain. Additional concern is expressed regarding the overall likelihood of obtaining the SIP and subsequent inferential decisions related to obtaining an SIP. Future research should examine more optimal cut scores or alternative methods for more accurately classifying patients in different clinical contexts and patterns of impairment.