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Table 4 Performance characteristics of corrected slack angle and slack angle for classifying different severity of spasticity based on optimal cutoff values

From: Reliability and diagnostic accuracy of corrected slack angle derived from 2D-SWE in quantitating muscle spasticity of stroke patients

Method MAS ≥ 1+ (95% CI) MAS ≥ 2 (95% CI) MAS ≥ 3 (95% CI)
Corrected slack angle
 Cutoff value 3.75 − 6.75 − 10.25
 AUROC 0.906 (0.691–0.990) 0.920 (0.709–0.993) 0.987 (0.808–1.000)
 Sensitivity (%) 93.75 (69.8–99.8) 80.00 (44.4–97.5) 100.00 (47.8–100.0)
 Specificity (%) 75.00 (19.4–99.4) 90.00 (55.5–99.7) 93.33 (68.1–99.8)
 PPV (%) 93.7 (68.6–99.9) 88.9 (48.9–99.8) 83.3 (31.1–99.8)
 NPV (%) 75.0 (13.2–99.8) 81.8 (46.3–98.1) 100.0 (76.8–100.0)
 LR+ 3.75 (2.1–6.7) 8.00 (5.5–11.6) 15.00 (13.1–17.2)
 LR− 0.083 (0.007–1.1) 0.22 (0.02–2.1) 0
Slack angle
 Cutoff value 0.25 − 3.25 − 6.75
 AUC 0.617 (0.377–0.822) 0.605 (0.365–0.813) 0.620 (0.379–0.824)
 Sensitivity (%) 93.75 (69.8–99.8) 80.00 (44.4–97.5) 80.00 (28.4–99.5)
 Specificity (%) 50.00 (6.8–93.2) 50.00 (18.7–81.3) 60.00 (32.3–83.7)
 PPV (%) 88.2 (62.6–98.7) 61.5 (31.6–86.1) 2.00 (1.1–3.7)
 NPV (%) 66.7 (4.0–99.8) 71.4 (25.8–97.2) 0.33 (0.05–2.1)
 LR+ 1.87 (0.7–5.0) 1.60 (0.8–3.2) 40.0 (12.2–73.8)
 LR− 0.13 (0.01–1.1) 0.40 (0.1–1.6) 90.0 (53.0–99.8)
  1. Data in parentheses are 95% confidence intervals
  2. MAS modified Ashworth scale, AUROC area under the receiver operator characteristic curve, PPV positive predictive value, NPV negative predictive value, LR+ positive likelihood ratio, LR− negative likelihood ratio