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2 × 2 table of spirometry for diagnosing airway obstruction in patients with asthma in lung function laboratory (all patients included with differentiation between asthma and COPD)
| asthma | no asthma | ||
| Spirometry + | 14 | 0 | |
| Spirometry - | 76 | 129 | |
| 219 | |||
| Pretest probability of having asthma 41% | |||
| Pretest probability of not having asthma 59% | |||
| Sensitivity | 16% (95%CI 10–24) | ||
| Specificity | 100% (95%CI 97–100) | ||
| PPV | 100% (95%CI 79–100) | ||
| NPV | 63% (95%CI 56–69) | ||
