The Orthostatic Discriminant and Severity Scale (ODSS): an assessment of orthostatic intolerance.

Purpose: To assess the ability of the Orthostatic Discriminant and Severity Scale (ODSS) to distinguish symptoms of orthostatic intolerance from non-orthostatic symptoms.

Methods: Clinical evaluations and questionnaire responses were collected in 73 healthy controls and 132 patients referred to the Autonomic Disorders Clinic from September 1, 2016, through April 30, 2018, for queries regarding autonomic dysfunction. A receiver operating characteristic (ROC) curve analysis was used to interpret sensitivity and specificity and to determine cutoff scores for symptom assessment. Inter-item reliability was assessed using Cronbach's alpha. To calculate positive and negative predictive powers, patient data were collected in a single-blinded fashion where the researcher collecting questionnaire data was blinded to the clinical evaluation and diagnosis. Predictive powers were calculated using a chi-squared cross-tabulation.

Results: The orthostatic and non-orthostatic symptoms scores produced ROC curves with an area under the curve of 0.89 and 0.79, respectively. The orthostatic scores yielded a positive and negative predictive power value of 73% and 81%, respectively. Combined, the ODSS identified patients with and without orthostatic symptoms with an overall accuracy of 76%. The reliability of the ODSS was significant, with a Cronbach's alpha of 0.88, and all dichotomous items were deemed worthy of retention following an inter-item reliability assessment.

Conclusions: The ODSS demonstrated a strong ability to distinguish patients with and without orthostatic intolerance and demonstrated sensitivity and specificity equivalent to that of other standardized measures. Overall, the ODSS produces symptom scores that are both reliable and useful for both research and clinical practice.