Initial validation of symptom scores derived from the orthostatic discriminant and severity scale.

ABSTRACT

OBJECTIVE: To develop a scale to quantify and discriminate orthostatic from non-orthostatic symptoms. In the current study, we present validation and reliability of orthostatic and non-orthostatic symptom scores taken from the orthostatic discriminate and severity scale (ODSS). METHODS: Validity and reliability were assessed in participants with and without orthostatic intolerance. Convergent validity was assessed by correlating symptoms scores with previously validated tools [autonomic symptom profile (ASP) and the orthostatic hypotension questionnaire (OHQ)]. Clinical validity was assessed by correlating scores against standardized autonomic testing. Test-retest reliability was calculated using an intra-class correlation coefficient. RESULTS: Convergent validity orthostatic (OS) and non-orthostatic (NS) symptom scores from 77 controls and 67 patients with orthostatic intolerance were highly correlated with both the orthostatic intolerance index of the ASP (OS r = 0.903; NS r = 0.651; p < 0.001) and the composite score of the OHQ (OS r = 0.800; NS r = 0.574; p < 0.001). Clinical validity symptom scores were significantly correlated with the total composite autonomic severity score (OS r = 0.458; NS r = 0.315; p < 0.001), and the systolic blood pressure change during head-up tilt (OS r = - 0.445; NS r = - 0.354; p < 0.001). In addition, patients with orthostatic intolerance had significantly higher symptom scores compared to controls (OS 66.5 ± 18.1 vs. 17.4 ± 12.9; NS 19.9 ± 11.3 vs. 10.2 ± 6.8; p < 0.001, respectively). Test-retest reliability Both orthostatic and non-orthostatic symptom scores were highly reliable (OS r = 0.956 and NS r = 0.574, respectively; p < 0.001) with an internal consistency of 0.978 and 0.729, respectively. INTERPRETATION: Our initial results demonstrate that the ODSS is capable of producing valid and reliable orthostatic and non-orthostatic symptom scores. Further studies are ongoing to test sensitivity, specificity and symptom severity.