Table 4. Accuracy of the COPD scale, the Vitalograph 6-SS test and the combination of both for COPD detection at indicated cut-off points observed in the 2010 Mexico City survey sample.
| GOLD stages 1–4 | GOLD stages 2–4 | FEV1/FEV6 <LLN | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Sensitivity (95% CI) | Specificity (95% CI) | Youden’s J (95% CI) | Sensitivity (95% CI) | Specificity (95% CI) | Youden’s J (95% CI) | Sensitivity (95% CI) | Specificity (95% CI) | Youden’s J (95% CI) | |
| COPD scale (score ≥10) | 91.7 (80.8–102.6) | 47.4 (43.5–51.3) | 0.39 (0.28–0.51) | 91.7 (75.6–107.7) | 46.7 (42.9–50.5) | 0.38 (0.22–0.55) | 82.4 (63.5–101.2) | 46.7 (42.8–50.7) | 0.29 (0.10–0.48) |
| Vitalograph COPD-6 6-SS (raw FEV1/FEV6 <80%) | 79.2 (63.0–95.3) | 86.3 (83.5–89.1) | 0.65 (0.49–0.82) | 75.0 (49.8–100.2) | 85.0 (82.0–88.0) | 0.60 (0.34–0.86) | 76.5 (57.0–95.9) | 85.5 (82.6–88.4) | 0.62 (0.42–0.82) |
| Positive to both tests (COPD scale and raw FEV1/FEV6 <8%) on 6-SS | 70.8 (53.8–87.9) | 89.6 (87.1–92.2) | 0.60 (0.43–0.78) | 66.7 (39.3–94.1) | 88.4 (85.6–91.2) | 0.55 (0.27–0.83) | 64.7 (42.8–86.6) | 88.8 (86.1–91.5) | 0.53 (0.31–0.76) |
Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; COV, coefficient of variation; FEV1, forced expiratory volume in 1s; FEV6, forced expiratory volume in 6s; GOLD, Global Initiative for Chronic Obstructive Lung Disease; LLN, lower limit of normal; 6-SS, 6-second spirometry.