Table 2. Diagnostic test characteristics of pre-BD FEV1/FEV6 <0.73 values from microspirometry versus post-BD FEV1/FVC from diagnostic spirometry for different cut-off points.
| Cut-off point |
All subjects (n=104)
|
Subjects referred for COPD (n=55)
|
||
|---|---|---|---|---|
| <0.70 | <LLN | <0.70 | <LLN | |
| NPV (95% CI) | 94.4 (86.4–98.5) | 96.3 (88.2–99.3) | 96.3 (88.3–99.8) | 96.3 (83.1–99.8) |
| PPV (95% CI) | 82.0 (73.3–86.3) | 56.0 (47.3–59.3) | 78.6 (66.1–82.0) | 57.1 (44.4–60.5) |
| Sensitivity (95% CI) | 93.2 (83.3–98.1) | 93.3 (78.8–98.8) | 95.7 (80.4–99.8) | 94.4 (73.1–99.7) |
| Specificity (95% CI) | 85.0 (77.8–88.6) | 70.3 (64.4–72.5) | 81.3 (70.3–84.2) | 68.4 (59.0–70.9) |
| Kappa | 0.77 (0.60–0.85) | 0.53 (0.36–0.60) | 0.75 (0.49–0.82) | 0.53 (0.27–0.60) |
Abbreviations: FEV1, forced expiratory volume in 1 s; FEV6, forced expiratory volume in 6 s; FVC, forced vital capacity; LLN, lower limit of normal; NPV, negative predictive value; PPV, positive predictive value.
Estimates are shown with 95% confidence intervals in parentheses.