Best cut-off EDV ratio for the detection of hemodynamic change and intracranial collaterals
| EDV ratio | Sensitivity | Specificity | PPV | NPV | |
|---|---|---|---|---|---|
| Poststenotic flow decrease (moderate) | 1.2 | 86 | 70 | 86 | 70 |
| Intracranial collateral flow | 1.2 | 72 | 63 | 89 | 36 |
| Stenosis ≧70% by NASCET | 1.2 | 83 | 75 | 88 | 67 |
| Stenosis ≧95% in area | 1.4 | 82 | 62 | 35 | 93 |
| Poststenotic flow decrease (severe) | 1.5 | 71 | 74 | 69 | 76 |
| Poststenotic narrowing | 1.6 | 76 | 71 | 57 | 85 |
Note.—PPV indicates positive predictive value; NPV, negative predictive value. Moderate decrease in poststenotic flow was defined as poststenotic flow <5 ml/s, since a poststenotic flow below 5 ml/s has been reported to be indicative of the development of intracranial collaterals (21). Severe decrease in poststenotic flow was also defined as <3.4 ml/s, the lower limit of 95% confidence interval. Poststenotic narrowing and severe stenosis were defined as the lower limit of 95% confidence interval. Best cut-off values of EDV ratio for predicting each hemodynamic change were obtained using receiver operator curve.