Validation of a screening questionnaire for X‐linked dystonia parkinsonism: The first phase of the population‐based prevalence study of X‐linked dystonia parkinsonism in Panay

Background The current prevalence of the condition is not yet known. No screening tool for the condition exists. By developing a questionnaire that may be used by community health workers, the study is intended to be the first step in identifying the prevalence of X-linked dystonia parkinsonism (XDP). Aim To develop and validate a simple, easy to use, community-based, screening questionnaire for the diagnosis of XDP Methods Community health workers administered an 11-item yes/no questionnaire, in the native Panay island language on 54 genetically-confirmed XDP patients and 54 healthy controls all from the island of Panay. The questionnaire is made up of elements from existing questionnaires on Parkinson's disease and dystonia, and known clinical features of XDP. The subjects were partitioned into training (n= 88) and test (n= 20) data sets. To select which items were predictive of XDP the Clinical Utility Index (CUI) of each item was determined. Afterwards, multivariable binary logistic regression was done to build a predictive model that was subsequently run on the test data set. Results Four items on ‘sustained twisting’, ‘jaw opening and closing’, ‘slowness in movement’ and ‘shuffling steps’ were found to be the most predictive of XDP. All had at least a ‘good’ CUI. The questions demonstrated 100% sensitivity and 90% specificity (95% CI: 65.6-100%) in identifying XDP suspects. Conclusion The resulting 4-item questionnaire was found to be predictive of XDP. The screening instrument can be used to screen for XDP in a large-scale population-based prevalence study. This article is protected by copyright. All rights reserved.