Table 4

Determination of cut-off levels and the area under the ROC curve

Cut-off point	Sensitivity (%)	Specificity (%)	Correctly classified (%)	LR-positive	LR-negative
≥3	100.00	0.00	66.47	1.00
≥4	100.00	3.51	67.65	1.04	0.00
≥5	100.00	8.77	69.41	1.10	0.00
≥6	98.23	14.04	70.00	1.14	0.13
≥7	97.35	19.30	71.18	1.21	0.14
≥8	94.69	29.82	72.94	1.35	0.18
≥9	93.81	33.33	73.53	1.41	0.19
≥10	92.92	38.60	74.71	1.51	0.18
≥11	92.04	47.37	77.06	1.75	0.17
≥12	88.50	49.12	75.29	1.74	0.23
≥13	86.73	56.14	76.47	1.98	0.24
≥14	81.42	63.16	75.29	2.21	0.29
≥15	78.76	66.67	74.71	2.36	0.32
≥16	76.99	68.42	74.12	2.44	0.34
≥17	73.45	77.19	74.71	3.22	0.34
≥18	67.26	84.21	72.94	4.26	0.39
≥19	61.06	85.96	69.41	4.35	0.45
≥20	55.75	89.47	67.06	5.30	0.49
≥21	53.10	92.98	66.47	7.57	0.50
≥22	49.56	92.98	64.12	7.06	0.54
≥23	45.13	94.74	61.76	8.57	0.58
≥24	41.59	94.74	59.41	7.90	0.62
≥25	36.28	94.74	55.88	6.89	0.67
≥26	33.63	94.74	54.12	6.39	0.70
≥28	28.32	98.25	51.76	16.14	0.73
≥29	27.43	98.25	51.18	15.64	0.74
≥30	23.89	98.25	48.82	13.62	0.77
≥31	23.01	98.25	48.24	13.11	0.78
≥33	20.35	98.25	46.47	11.60	0.81
≥34	17.70	98.25	44.71	10.09	0.84
≥35	16.81	98.25	44.12	9.58	0.85
≥36	15.93	98.25	43.53	9.08	0.86
≥37	12.39	98.25	41.18	7.06	0.89
≥38	11.50	98.25	40.59	6.56	0.90
≥39	10.62	98.25	40.00	6.05	0.91
≥40	8.85	98.25	38.82	5.04	0.93
≥41	6.19	98.25	37.06	3.53	0.95
≥45	6.19	100.00	37.65		0.94
≥46	5.31	100.00	37.06		0.95
≥49	3.54	100.00	35.88		0.96
≥50	2.65	100.00	35.29		0.97
≥58	1.77	100.00	34.71		0.98
≥68	0.88	100.00	34.12		0.99
≥69	0.00	100.00	33.53		1.00

Area under the receiver operating characteristic (ROC) curve was 0.82, and SE was 0.033 (95% CI 0.75 to 0.89).
LR, likelihood ratio.