Physiological and clinical comparison of active stand and head-up tilt tests in Postural Orthostatic Tachycardia Syndrome (POTS)
Bibliographic record
Abstract
Head-up tilt (HUT) and active stand tests (AST) are used in the diagnosis of Postural Orthostatic Tachycardia Syndrome (POTS), but their relative diagnostic accuracy is unclear. This necessitates a direct comparison under standardized conditions. We aimed to compare the hemodynamic responses and diagnostic accuracy of AST vs. HUT in POTS. To address this, patients with POTS ( n = 60) completed a 10-min AST followed by HUT on the same day. Beat-to-beat hemodynamics were recorded during 10-min supine baselines and each test. Delta values were calculated for each test (upright 1-min averages minus baseline average). Δ[heart rate] increased significantly over time (1_Min: 28 bpm to 10_Min: 40 bpm; P Time < 0.001), and was greater for HUT (33 bpm vs. 37 bpm; P ASTvHUT = 0.01), with significant Time x Condition interaction (38 bpm vs. 42 bpm at10min; P INT < 0.001). Δ[stroke volume] declined over time (1_Min: -18 ml to 10_Min: -32 ml); P Time < 0.001), with no significant test or interaction effects (P ASTvHUT = 0.36; P INT = 0.21). Δ[SBP] decreased (1_Min: −0.3 mmHg to 10_Min: −5.7 mmHg); P Time < 0.001) over time, with no test or interaction effects. Fewer patients met POTS heart rate criteria during the AST (AST: 74 % vs. HUT: 98 %; p < 0.001). Lowering the threshold to 27 bpm for AST narrowed the gap but was still significantly higher for HUT (AST: 83 % vs HUT: 98 %; p = 0.02). Orthostatic tachycardia differs between AST and HUT in patients with POTS. The proportion of patients with POTS meeting the heart rate diagnostic criteria differs significantly between AST and HUT, a discrepancy that can be mitigated by lowering the heart rate threshold for the AST.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".