The Comparative Usefulness of Orthostatic Testing and Tilt Table Testing in the Evaluation of Autonomic-Associated Dizziness

OBJECTIVE: To elucidate the usefulness of clinical orthostatic blood pressure testing (COBP) as a screening tool for autonomic dysfunction. STUDY DESIGN: In this retrospective case review, the records of 156 consecutive patients with nonotologic dizziness as the primary complaint seen in an academic neurotology clinic between 2005 and 2009 were reviewed. The objective of this study was accomplished by comparing the diagnostic yield of COBP with that of head-upright tilt table testing (HUT) and assessing the sensitivity and specificity of COBP in predicting an abnormal HUT in patients with nonotologic dizziness. SETTING: Ambulatory tertiary referral center. PATIENTS: Patients presenting to the clinic with dizziness without otologic cause. INTERVENTION(S): Clinical evaluation, orthostatic blood pressure testing, and HUT. MAIN OUTCOME MEASURE(S): The primary outcome assessed in this study was patient blood pressure. Blood pressures were measured in the clinic in the following order: supine, sitting, and standing. Positive COBP was defined as a reduction in systolic or diastolic blood pressure greater than 20 or 10 mm Hg, respectively, or both, within 3 minutes of sitting from supine or standing from sitting. For comparison, HUT was used as the gold standard. A positive HUT was defined as a reduction in systolic or diastolic blood pressure greater than 20 or 10 mm Hg, respectively, or both, relative to baseline at any point after initiation of HUT. RESULTS: Forty patients were referred for HUT. Twenty-four (61.5%) of these patients were deemed to have a positive response. Thirty-three patients (85%) referred to HUT were initially evaluated with COBP, which revealed orthostatic hypotension (OH) in 8 patients (24%). COBP was calculated to have sensitivity and specificity of 21% and 71%, respectively, when asymptomatic OH was included in the positivity criteria. When asymptomatic OH was excluded from the positivity criteria, the sensitivity and specificity remained similar at 25% and 76%, respectively. However, the exclusion of asymptomatic OH from the positivity criteria resulted in a decrease in the positive predictive value from 50% to 25% and an increase in the negative predictive value from 40% to 76%. Overall, HUT detected 16 patients with an abnormal result that were missed by COBP testing. CONCLUSION: Evaluation for autonomic dysfunction should be part of the comprehensive evaluation of a dizzy patient, involving, at a minimum, orthostatic testing of blood pressure and heart rate. Patients with nonotologic dizziness and light-headedness with a normal neurotologic evaluation can reasonably be referred for HUT, even in the presence of normal in-office orthostatic testing.