Table 1.
Clinical indicators used to differentiate POTS from VVS.
| Cut-Off | Sensitivity | Specificity | Year | |
|---|---|---|---|---|
| Plasma H2S level | 98 μmol/L | 90% | 80% | 2012 |
| Serum iron level | 11.8 μmol/L, | 92.50% | 64.70% | 2013 |
| AI and 30/15 | AI: 28.180; 30/15: 1.025 |
95.80% | 80.80% | 2018 |
| dULF | 36.2 ms2 | 71.40% | 75.00% | 2019 |
POTS: postural tachycardia syndrome; VVS: vasovagal syncope; AI: Acceleration Index; dULF: daytime ultra-low frequency; 30/15: ratio of the R-R interval length between the 30th and 15th beats in the upright position.