Table 3 Comparison of screening performances in four scoring system
|  | Wells | Wells + D-Dimer | Wells + PERC | PECSS | PECSS + D-Dimer | PECSS + PERC |
|---|---|---|---|---|---|---|
Primary endpoint | ||||||
 Failure rate in severe PE | 5.1% | 0.9% | 0.0% | 0.0% | 0.3% | 0.0% |
Secondary endpoints | ||||||
 Failure rate in moderate PE | 16.5% | 4.3% | 0.0% | 2.2% | 4.3% | 0.0% |
 Failure rate in mild PE | 16.0% | 6.4% | 1.1% | 0.0% | 6.4% | 0.0% |
 Failure rate in any PE | 9.6% | 2.9% | 0.2% | 0.5% | 2.2% | 0.0% |
Additional endpoints | ||||||
 Sensitivity | 90.4% | 97.1% | 99.8% | 99.5% | 97.8% | 100.0% |
 Specificity | 66.7% | 9.8% | 7.4% | 25.5% | 52.0% | 4.5% |
 NPV | 95.9% | 91.9% | 99.3% | 99.4% | 98.7% | 100.0% |
 PPV | 44.9% | 24.3% | 24.3% | 28.4% | 37.7% | 23.8% |