Objective: To assess investigators’ level of agreement with centrally adjudicated SWEDDs based on dopamine transporter imaging (qualitatively defined) during screening of subjects whom investigators had diagnosed with probable Parkinson’s disease (PD).

Background: Prior studies have reported up to 20% of de novo PD participants had a SWEDD. The inclusion of subjects with a SWEDD, who are thought to have a low likelihood of having PD, undermines the power of PD trials. SURE-PD3 is the first PD trial to include dopamine transporter imaging as a screening procedure to enrich for PD by excluding individuals with a SWEDD.

Method: We surveyed site investigators who screened a subject with a SWEDD after trial conclusion. Investigators were invited via email to give consent and complete a questionnaire on the follow-up care and neurological diagnosis of these subjects. Respondents were asked to estimate the probability of PD and their current agreement with the originally unexpected screening SWEDD result.

Results: In the SURE-PD3 study, 30 subjects at 20 sites had a SWEDD (comprising 10% of subjects with a screening scan from 34% of enrolling sites). We received complete questionnaire data on 16 (53%) of these subjects. Investigators disagreed with the SWEDD diagnosis in 8 subjects (50%). Reasons included the presence of one or more of: progressive parkinsonian syndrome with no other cause, dopamine responsiveness, local review of the screening scan, or a separate scan that was abnormal. Importantly, only seven of the 16 subjects received clinical follow-up with their respective site investigator, with a mean follow-up of 1.5 years after the screening scan. Investigators were confident of a PD diagnosis for 2 of these 7 subjects (29%). The other 5 were diagnosed as essential tremor (n=1), dopa-responsive dystonia (n=1), MSA (n=1), and psychogenic disorder (n=2).

Conclusion: Our study demonstrated a moderate level of residual disagreement among investigators regarding their subject’s SWEDD diagnosis. Among a small sample of subjects followed clinically, a third may represent false negative determinations.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/site-investigator-perspectives-on-exclusionary-determinations-of-swedds-scans-without-evidence-of-dopaminergic-deficit-during-screening-in-the-sure-pd3-study/