Factors associated with true-positive and false-positive diagnoses of behavioural variant frontotemporal dementia in 100 consecutive referrals from specialist physicians.

Background: The behavioural variant of frontotemporal dementia (bvFTD) is a challenging diagnosis due to overlapping symptoms with psychiatric and other neurological conditions. Accordingly, misdiagnosis is common. The present study aimed to identify clinical factors contributing to misdiagnoses of bvFTD by specialist physicians.

Methods: We retrospectively analysed 100 consecutive referrals by specialist physicians (primarily psychiatrists, neurologists and geriatricians) to a tertiary cognitive disorders clinic specializing in frontotemporal lobar degenerative disorders. Patients were included if the referring specialist suspected bvFTD or if bvFTD was confirmed as the final diagnosis. Diagnostic factors were assessed by comparing the initial referral information with final clinical diagnoses.

Results: Of the 100 patients, 34 were true-positive and 66 were false-positive for bvFTD. False-positive diagnoses were often based on misinterpretation of neuroimaging, particularly nuclear imaging (FDG-PET and HMPAO-SPECT), where subjective interpretation errors led to incorrect bvFTD diagnoses in 32 patients. Cognitive testing also contributed to misdiagnosis, with formal neuropsychological testing incorrectly leading to a bvFTD diagnosis in 20 patients. Patients with prior psychiatric histories were more likely to be misdiagnosed. Observable behavioural features of bvFTD and physical neurological signs were significantly more prevalent in true-positive patients.

Conclusions: Misinterpretation of neuroimaging and cognitive testing, in particular formal neuropsychological testing, significantly contributed to false-positive bvFTD diagnoses. Physicians should be cautious not to over-interpret neuroimaging and neuropsychology studies and be wary of patients with prior psychiatric histories. In contrast, greater weight should be placed on objective clinical observations of behavioural signs of bvFTD and the emergence of physical neurological signs.