P.032 Development of a new instrument to discriminate orthostatic from non-orthostatic symptoms

Background: Orthostatic symptoms including dizziness, light-headedness and syncope can be major causes of disability in patients with dysautonomia. Currently there is no validated tool capable of discriminating orthostatic from non-orthostatic constitutional symptoms. Therefore, we developed the Orthostatic Discriminant and Severity Scale (ODSS) to help make this distinction. Objective: Demonstrate validity and reliability of the ODSS. Methods: Convergent and clinical validity were assessed by correlating Orthostatic scores with previously validated tools (Autonomic Symptom Profile (ASP), composite scores of the Orthostatic Hypotension Questionnaire and the total Composite Autonomic Severity Score (tCASS), respectively). Test-retest reliability was calculated using an intra-class correlation coefficient. Results: Orthostatic scores from 23 controls and 5 patients were highly correlated with both the Orthostatic Intolerance index of the ASP (r=0.724;p<0.01) and the composite OHDAS and OHSAS (r=0.552;p<0.01 and r=0.753;p<0.01, respectively), indicating good convergent validity. Orthostatic scores were significantly correlated with tCASS (r=0.568;p<0.01), and the systolic blood pressure change during head-up tilt (r=-0.472;p=0.013). In addition, patients with Neurogenic Orthostatic Hypotension had significantly higher Orthostatic scores than controls (p<0.01) indicating good clinical validity. Test-retest reliability was strong (r=0.954;p<0.01) with an internal consistency of 0.978. Conclusions: Our results, though preliminary, provide empiral evidence that the ODSS is capable of producing a valid and reliable orthostatic score.