Objective: To develop a revised and improved version of the FXTAS-RS.

Background: Accurate measurement of FXTAS motor symptoms is vital to provide valid and reliable clinical and research assessment. The clinimetric analysis of the first version of the FXTAS-RS demonstrated the need for improvements (1).

Method: This is a clinimetric study conducted using a Delphi technique. A panel of nine multidisciplinary specialists in neurology (physicians, psychologists and nurses), with clinical and/or research expertise with patients with FXTAS participated in five-round virtual meetings throughout the year of 2020. The aims for each round were as follows: Round 1 – List the domains, subdomains and scale items. Round 2 – To establish consensus (using the content validity ratio of ≥ 0.75) on the set of domains and subdomains previously listed. Round 3 – Assess whether the items composing the first version of FXTAS-RS are contained in the domains of interest identified in the previous round; and analyze the items presenting weaknesses in the previous clinimetric analyzes, establishing a consensus on which ones should be maintained, improved, or excluded. Round 4 – Develop and establish agreement on the most appropriate type of response options and anchors of the scale. Round 5 – Review the draft rating instrument and vote on the second version of the FXTAS-RS.

Results: In Round 1, six domains (tremor, parkinsonism, ataxia, eye moment disorders, dystonia and neuropathy) and 65 subdomains of observable FXTAS motor symptoms were listed by the experts for an evaluation of the items composing the first version. In Round 2, consensus was established for five domains (with the exception of neuropathy) and 20 subdomains. In Round 3, of the 61 items composing the first version of the FXTAS-RS, 14 were excluded and 21 were analyzed on their clinimetric weakness. Panelists established consensus to keep 26 items for the second version of the FXTAS-RS, covering all domains emerging from Round 1. In Round 4, they established consensus on the response options and anchors of the observer-reported outcome. In Round 5, the scale was revised, instructions for use were created and the second version of FXTAS-RS was established.

Conclusion: The second version of FXTAS-RS was created with 26 items, most containing five well-anchored response options. For the next steps we will conduct cognitive pre-testing and pilot validation tests.

References: Hall DA, Stebbins GT, Jacquemont S, Berry‐Kravis E, Goetz CG, Hagerman R, et al. Clinimetric Properties of the Fragile X‐associated Tremor Ataxia Syndrome Rating Scale. Mov Disord Clin Pract. 2019;6(2):120–4.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/fragile-x-associated-tremor-ataxia-syndrome-rating-scale-fxtas-rs-development-process-using-the-delphi-method/