Table 1 Determination of the cut-off level and the ROC area under the curve
Cut-off pointSensitivity (%)Specificity (%)Correctly classified (%)LR+LR−
(⩾3)100.00.045.31.00
(⩾4)100.06.949.11.070.00
(⩾5)100.010.350.91.120.00
(⩾6)100.013.852.81.160.00
(⩾7)100.020.756.61.260.00
(⩾8)100.031.062.31.450.00
(⩾9)100.034.564.21.530.00
(⩾12)100.037.966.01.610.00
(⩾13)95.844.867.91.740.09
(⩾14)95.855.273.62.140.08
(⩾15)91.765.577.42.660.13
(⩾16)87.572.479.33.170.17
(⩾17)87.575.981.33.630.17
(⩾18)83.382.883.04.830.20
(⩾20)79.286.283.05.740.24
(⩾21)75.089.783.07.250.28
(⩾22)70.889.781.16.850.33
(⩾23)62.589.777.46.040.42
(⩾24)54.293.175.57.850.49
(⩾25)54.296.677.415.710.48
(⩾26)50.096.675.514.500.52
(⩾27)45.896.673.613.290.56
(⩾29)37.596.669.810.880.65
(⩾30)33.396.667.99.670.69
(⩾31)25.096.664.27.250.78
(⩾34)20.896.662.36.040.82
(⩾36)8.396.656.62.420.95
(⩾41)4.296.654.71.210.99
(⩾46)4.2100.056.60.96
(>46)0.0100.054.71.00
  • Area under the ROC curve 0.889, standard error 0.047 (95% CI 0.797 to 0.980).

  • LR, likelihood ratio; ROC, receiver operating characteristic.