Abstract Details

Title Comparison of Skin Biopsy Immunofluorescence and CSF Seed Amplification Assay of Pathological Alpha-synuclein in Patients with Parkinsonism or RBD

Topic Movement Disorders

Presentation(s) P6 - Poster Session 6 (5:00 PM-6:00 PM)

Poster/Presentation
Number 16-009

Objective To compare results of skin biopsy alpha-synuclein immunofluorescence (αS-IF) assay with CSF alpha-synuclein seed amplification (αS-SAA) assay in a subset of patients with parkinsonism or RBD.

Background In Arizona, the Syn-One test for cutaneous αS has been commercially available since late 2019, whereas the SAAmplify (aka SYNTap) test for CSF αS became commercially available only in early 2025. There is a dearth of studies that compare results of cutaneous αS-IF with CSF αS-SAA. In a study of 41 RBD patients, cutaneous αS-IF showed 89% diagnostic accuracy compared to 69% for CSF αS-SAA. In another study of 90 patients fulfilling diagnostic criteria for synucleinopathies and non-synucleinopathies, both IF and RT-QuIC (a form of SAA) of skin and CSF showed high sensitivity and specificity in discriminating synucleinopathies from non-synucleinopathies.

Design/Methods We retrospectively reviewed charts of all patients who have undergone both skin biopsy and CSF assay of αS from 2019-2025 in one movement disorders center.

Results We identified 36 patients who have undergone both cutaneous αS-IF and CSF αS-SAA for either parkinsonism or RBD. 11 were female, 25 were male. For all 36, skin biopsy preceded CSF tap by a mean of 28 months (SD=22.76). Results were concordant for 17/36 (47%) and discordant for 19/26 (53%). Of the 17 concordant cases, 4/17 (24%) were αS(+) for both skin and CSF, whereas 13/17 (76%) were αS(-) for both. Of the 19 discordant cases, 16/19 (84%) were αS(+) in skin but αS(-) in CSF, whereas 3/19 (15%) were αS(-) in skin but αS(+) in CSF. In 15/36 (42%) of patients, the diagnosis was altered after CSF αS-SAA.

Conclusions The diagnostic accuracy may be increased by comparing results of cutaneous αS-IF with CSF αS-SAA in patients with suspected clinical or prodromal synucleinopathy where the diagnosis remains unclear. Larger prospective studies are indicated.

Authors/Disclosures
Virgilio Gerald H. Evidente, MD, FAAN (Movement Disorders Center of Arizona) PRESENTER	Dr. Evidente has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Revance. Dr. Evidente has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Abbvie. Dr. Evidente has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Teva. Dr. Evidente has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Medtronic. Dr. Evidente has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Neurocrine. Dr. Evidente has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Amneal. Dr. Evidente has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Abbvie. The institution of Dr. Evidente has received research support from CND. The institution of Dr. Evidente has received research support from Aeon. The institution of Dr. Evidente has received research support from Bukwang Pharmaceuticals. The institution of Dr. Evidente has received research support from Jazz Pharmaceuticals. The institution of Dr. Evidente has received research support from Scion Neurostim. The institution of Dr. Evidente has received research support from Theravance Biopharma. Dr. Evidente has received research support from Cerevance. Dr. Evidente has received research support from Ipsen.
Danica Evidente	Danica Evidente has nothing to disclose.
Rebecca Johnson, Research Coordinator and MA	Miss Johnson has nothing to disclose.
Danielle G. Drake, MA	Mrs. Drake has nothing to disclose.

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