Let's lower the floor: Clinical utility of the D-KEFS TMT with a forensic psychiatric inpatient population

Trail-making tests are widely used as part of neuropsychological assessments, although the prevalence of processing speed deficits in schizophrenia spectrum disorders may limit their utility when administered to this population. In response, our study sought to explore D-KEFS TMT performance among a forensic-oriented schizophrenia spectrum sample, with the goal of generating normative data to enhance the utility of the TMT with this population. Archival data was collected from a sample of patients admitted to a forensic maximum-security psychiatric facility. Analyses revealed a large percentage of individuals achieved an "impaired" result across D-KEFS TMT trials, ranging from 20% to more than 60%. The most noteworthy finding was for Number-Letter Switching, in which approximately 48% of participants performed at the floor level. Following reclassification of performance, 36% of our sample were identified as "below average," while greater than 60% of individuals were captured as average to above average. The current analyses revealed a problematic skew in TMT performance among schizophrenia spectrum patients, in turn complicating interpretation of cognitive status as well as the ability to compare performance between patients and over time. The present adjustments account for this skew and yield more variability in standardized scoring.