Test-retest reliability of clinical supine-to-stand tests in patients with postural orthostatic tachycardia syndrome: A cautionary tale

Postural orthostatic tachycardia syndrome (POTS) is a debilitating form of orthostatic intolerance that predominantly (∼90%) affects young women, leading to diminished quality of life. Challenges associated with POTS are compounded by lengthy diagnostic delays on the order of years, repeated visits to multiple physicians, and misdiagnoses. Fundamental criteria for diagnosing POTS are (1) experiencing orthostatic symptoms (eg, lightheaded, dizzy, nausea, and heart palpitations) that improve with recumbency for at least 3–6 months and (2) a sustained increase in heart rate (HR) of ≥30 beats/min within 5–10 minutes of standing in the absence of hypotension (≥40 beats/min for people younger than 19 years). Given the nonspecific nature of patients’ symptomology, orthostatic tachycardia in the absence of hypotension is heavily relied on for diagnosis. However, inconsistency of HR responses to orthostatic stress tests conducted in clinical settings may contribute to diagnostic delays and misdiagnoses experienced by many individuals. To characterize this variability, we conducted 2 supine-to-stand tests to assess the test-retest reliability (ie, consistency) of HR responses to clinical orthostatic stress tests in people with POTS.