Accuracy of FDG-PET brain scan to differentiate sporadic bvFTD of mild severity from late onset psychiatric disorders.

BACKGROUND

Positron emission tomography with [18F] fluorodeoxyglucose (FDG-PET) brain scan accurately differentiates behavioral variant frontotemporal dementia (bvFTD) from other neurodegenerative disorders. However, the accuracy of FDG-PET to differentiate bvFTD from primary psychiatric disorders (PPD) remains understudied, with prior studies reporting high false positive rates.

METHODS

Retrospective data from the DIagnostic and Prognostic Precision Algorithm for behavioral variant Frontotemporal Dementia (DIPPA-FTD) database included 508 sporadic bvFTD and 152 late-onset PPD cases (onset at age 45-75 years). 226 cases had an FDG-PET scan completed at baseline with a visual rating for bvFTD diagnosis (Yes, No, or Ambiguous). Follow-up clinical diagnosis at least 1 year later was used as the gold standard to calculate sensitivity and specificity of FDG-PET at baseline.

RESULTS

Follow up consisted of 198 probable bvFTD cases (87.6%) and 28 PPD cases (12.4%). FDG-PET had a sensitivity of 87% and a specificity of 93% to identify bvFTD cases, with a diagnostic accuracy of 88%. Within the PPD group, 7.1% had false positives and 14.3% had ambiguous scans. Rates of false negatives (normal or ambiguous PET) in bvFTD were 13.1% and were 2.6 times more common in males.

CONCLUSION

FDG-PET had excellent diagnostic accuracy to differentiate between sporadic bvFTD and late onset PPD, with a low true false positive rate in PPD. False negatives were more common in males with bvFTD. These results support the use of FDG-PET as an important step in the diagnostic algorithm for patients with late onset behavioral changes, although results can be misleading in some cases.