Background: There is no widely accepted validated scale to assess the comprehensive symptom burden and severity of neurogenic orthostatic hypotension (NOH). The Orthostatic Hypotension Questionnaire (OHQ) was developed, with two components: the six-item symptoms assessment scale and a four-item daily activity scale to assess the burden of symptoms. Validation analyses were then performed on the two scales and a composite score of the OHQ.
Methods: The validation analyses of the OHQ were performed using data from patients with NOH participating in a phase IV, double blind, randomized, cross over, placebo-controlled trial of the alpha agonist midodrine. Convergent validity was assessed by correlating OHQ scores with clinician global impression scores of severity as well as with generic health questionnaire scores. Test-retest reliability was evaluated using intraclass correlation coefficients at baseline and crossover in a subgroup of patients who reported no change in symptoms across visits on a patient global impression scores of change. Responsiveness was examined by determining whether worsening or improvement in the patients' underlying disease status produced an appropriate change in OHQ scores.
Results: Baseline data were collected in 137 enrolled patients, follow-up data were collected in 104 patients randomized to treatment arm. Analyses were conducted using all available data. The floor and ceiling effects were minimal. OHQ scores were highly correlated with other patient reported outcome measures, indicating excellent convergent validity. Test-retest reliability was good. OHQ scores could distinguish between patients with severe and patients with less severe symptoms and responded appropriately to midodrine, a pressor agent commonly used to treat NOH.
Conclusion: These findings provide empirical evidence that the OHQ can accurately evaluate the severity of symptoms and the functional impact of NOH as well as assess the efficacy of treatment.