Can standing replace upright tilt table testing in the diagnosis of postural tachycardia syndrome (POTS) in the young?

Purpose: We compared standing and upright tilt in patients with postural tachycardia syndrome (POTS) and healthy volunteers to determine whether standing accurately tests for POTS in youngsters < 19 years. POTS in adolescents is defined by orthostatic intolerance plus sustained excessive upright tachycardia, without hypotension during upright tilt. We examined whether active standing is a valid classifier for POTS in adolescents compared to tilt.

Methods: Patients with POTS (N = 36, 12.2-18.8 years) and healthy volunteers (N = 39, 13.1-18.9 years) performed stand for a minimum of 5-min and were tilted to 70° for 10 min. Receiver operating characteristics analyses (ROC) were performed at 5-min stand, and at 5  and 10 min tilt for optimal threshold for heart rate (HR) increase (ΔHR), and test sensitivity and specificity.

Results: Most subjects were unable to stand for 10 min. ΔHRs at 5 min stand were higher in POTS (31 ± 3) compared with control (21 ± 2) and elevated at 5- or 10-min tilt in POTS (51 ± 3 and 51 ± 2) versus control (26 ± 2 and 25 ± 2) compared with standing. ΔHR in POTS and controls for 10 min were not different from 5 min. For 5 min stand ROC threshold was 26 beats per min (bpm), sensitivity of 70.6%, and specificity of 68.2% compared with 39 bpm, 88.2%, and 95.1% for 5 min tilt, and 40 bpm, 94.1%, and 95.1% for 10-min tilt. A precision-recall graph confirmed the superior discriminating ability of 5 min and 10 min tilt compared to 5 min stand.

Conclusions: The stand test is relatively non-specific and imprecise compared to tilt and does not satisfactorily distinguish POTS from control in patients aged < 19 years old.