Towards uniformity in bvFTD Phenocopy Syndrome: specialists’ perspectives and proposed research criteria
Bibliographic record
Abstract
BACKGROUND: The phenocopy syndrome of behavioral variant FTD (phFTD) refers to patients exhibiting clinical characteristics of bvFTD but without objective progression during follow-up. As no diagnostic criteria currently exist, we aimed to assess clinicians' perspectives on the diagnostic process for phFTD. By integrating these perspectives, we aim to develop research criteria for phFTD. METHOD: We established the Phenocopy Working Group within the Neuropsychiatric International Consortium on Frontotemporal Dementia (NIC-FTD), a consortium of researchers with expertise in FTD and psychiatric disorders. We employed an international Delphi methodology comprising three rounds, each involving an online survey followed by a group meeting to discuss controversies. Here we present the results of the first round. We recently sent out the second-round survey, in which we aim to reach consensus on the remaining categories, incorporating clinical presentation, diagnostic tools and follow-up. In a third and final round we will establish consensus on the final criteria. RESULT: The expert panel of the first Delphi round consisted of 50 clinicians with a median of 10 (IQR: 5-20) years of experience in phFTD. According to panelists' estimations, Raskovsky (2011) criteria most frequently met in phFTD were apathy (90%), loss of empathy (64%) and disinhibition (60%). Additionally, memory complaints and depressive symptoms were considered often present. Genetic screening for C9orf72 was almost unanimously endorsed, as were structural MRI and [18F]-FDG-PET as minimally required neuroimaging (Figure 1). Most frequent differential diagnoses were bvFTD (76%), mood disorders (48%), personality disorders (32%) and bvAD (24%) (Figure 2). Two thirds of panelists presumed the likelihood of a neurodegenerative etiology for phFTD to be ≤50% (Figure 3). 85% considered clinical follow-up of at least two years appropriate before appointing a label of phFTD. CONCLUSION: The first Delphi round showed expert consensus on several components of the diagnostic process for phFTD, including genetic testing for C9orf72, baseline and repeated structural MRI and FDG-PET and follow-up duration. Completing the full Delphi procedure will result in a set of research criteria. Establishment of these criteria will enhance accurate identification of phFTD, facilitate research and advance clinical care for this rare and poorly understood patient group.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.382 | 0.323 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.008 | 0.005 |
| Science and technology studies | 0.006 | 0.017 |
| Scholarly communication | 0.010 | 0.013 |
| Open science | 0.006 | 0.019 |
| Research integrity | 0.008 | 0.007 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".