Dataset for the discrepancy between letter and semantic fluency as a neurocognitive marker

Objectives. The discrepancy between letter fluency and semantic fluency has been proposed as a useful marker in neurocognitive diagnostics. No studies to date have examined discrepancy across different cognitive disorders in real world clinical settings. We aimed to assess the utility of a discrepancy score between letter fluency and semantic fluency in accurately classifying between several neurocognitive disorders.Methods. 479 patients diagnosed with a neurocognitive disorder who had undergone neuropsychological assessment were recruited retrospectively from four clinical services at a tertiary hospital in Melbourne, Australia. Letter and semantic fluency scores were re-normed based on a control group, and a scaled subtraction discrepancy score was computed. Differences across diagnoses were assessed using general linear models (GLMs). Classification accuracy was assessed using receiver operating characteristic (ROC) curves.Results. Across the entire sample, the most common pattern was of normal performance on both letter and semantic fluency (n = 257, 53.7%). An impairment on both fluency measures (n = 96, 20.1%) was similar in frequency to an impairment in one paradigm only (n = 126, 26.2%). No differences between the diagnostic groups were observed based on the discrepancy score, and whilst there was a very modest discrimination ability in dementia of the Alzheimer type, it did not prove useful in accurately classifying other disorders from controls.Conclusion. This study did not support the use of a psychometric discrepancy score as a useful diagnostic metric, particularly in the absence of clinical interpretation. Further research is needed to determine in which clinical contexts, if any, such a psychometric marker is diagnostically useful when interpreted in isolation.