Table 4. Reliability of intraoperative EPs with the new cutoff compared to that for the pre-existing alarm criteria

Variables No. Sensitivity (%) Specificity (%) PPV (%) NPV (%)
Adjusting the pre-existing alarm criteria
 ΔSEPLat >10%
  Total 4 8.3 96.7 25.0 89.0
   Vascular 3 0.0 95.2 0.0 98.3
   Tumor 1 9.1 100.0 100 75.0
 ΔMEPAmp >50%
  Total 6 16.7 95.7 33.3 89.8
   Vascular 1 0.0 98.4 0.0 98.4
   Tumor 5 18.2 90.0 40.0 75.0
 ΔSEPLat >10% or ΔMEPAmp >50%
  Total 9 25.0 93.5 33.3 90.5
   Vascular 3 0.0 95.2 0.0 98.3
   Tumor 6 27.3 90.0 50.0 77.1
Adjusting the new cutoff
 ΔSEPLat >7.1%
  Total 27 66.7 79.3 29.6 94.8
   Vascular 13 100.0 80.6 7.7 100.0
   Tumor 14 63.6 76.7 50.0 85.2
 ΔMEPAmp >21.0%
  Total 52 91.7 55.4 21.2 98.1
   Vascular 30 100.0 53.2 3.3 100.0
   Tumor 22 90.9 60.0 45.5 94.7
 ΔSEPLat >7.1% or ΔMEPAmp >21.0%
  Total 64 91.7 42.4 17.2 97.5
   Vascular 38 100.0 40.3 2.6 100.0
   Tumor 26 90.9 46.7 38.5 93.3
PPV: positive predictive value; NPV: negative predictive value; ΔSEPLat: latency change of somatosensory evoked potential; ΔMEPAmp: amplitude change of motor evoked potential.