Table 3—

Sensitivity, specificity and Youden’s index of the various forced expiratory volume in 1 s/forced vital capacity fixed cut-off points^# by sex

Cut-off	Sensitivity	Specificity	Youden’s index
Males
0.70	76.5 (69.9–82.0)	100.0 (98.4–100.0)^¶	0.76
0.71	83.2 (75.5–88.8)	100.0 (98.4–100.0)^¶	0.83
0.72	89.9 (82.1–94.6)	99.2 (94.0–99.9)	0.89
0.73	95.8 (90.2–98.3)	97.9 (94.2–99.2)	0.94
0.74	99.2 (94.0–99.9)	95.3 (90.9–97.7)	0.94
0.75	100.0 (96.9–100.0)^¶	92.4 (86.5–95.8)	0.92
0.76	100.0 (96.9–100.0)^¶	87.7 (81.4–92.1)	0.88
0.77	100.0 (96.9–100.0)^¶	80.9 (74.3–86.2)	0.81
0.78	100.0 (96.9–100.0)^¶	78.8 (72.8–83.8)	0.79
0.79	100.0 (96.9–100.0)^¶	69.5 (63.4–75.0)	0.69
0.80	100.0 (96.9–100.0)^¶	58.1 (51.6–64.3)	0.58
Females
0.70	57.3 (49.5–64.7)	100.0 (98.9–100.0)^¶	0.57
0.71	68.4 (58.7–76.7)	100.0 (98.9–100.0)^¶	0.68
0.72	72.6 (63.0–80.5)	100.0 (98.9–100.0)^¶	0.73
0.73	84.6 (77.7–89.7)	99.4 (97.6–99.9)	0.84
0.74	88.0 (82.4–92.0)	98.0 (96.1–98.9)	0.86
0.75	91.5 (87.4–94.3)	95.9 (93.0–97.7)	0.87
0.76	95.7 (91.3–98.0)	92.1 (88.8–94.5)	0.88
0.77	98.3 (94.0–99.5)	88.3 (84.0–91.6)	0.87
0.78	100.0 (96.9–100.0)^¶	84.3 (79.4–88.1)	0.84
0.79	100.0 (96.9–100.0)^¶	79.3 (74.0–83.7)	0.79
0.80	100.0 (96.9–100.0)^¶	72.9 (67.6–77.6)	0.73

Data are presented as % (95% confidence interval), unless otherwise stated. ^#: using the lower limit of normal as the gold standard for defining airflow obstruction during European Community Respiratory Health Survey I; ^¶: exact one-sided 97.5% confidence interval.