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2 × 2 table of spirometry for diagnosing airway obstruction in patients with asthma in general practice (n = 168; patients with COPD excluded)
| asthma | no asthma | ||
| Spirometry + | 26 | 8 | |
| Spirometry - | 63 | 71 | |
| 168 | |||
| Pretest probability of having asthma 41% | |||
| Pretest probability of not having asthma 59% | |||
| Sensitivity | 29% (95%CI 21–39) | ||
| Specificity | 90% (95%CI 81–95) | ||
| PPV | 77% (95%CI 60–88) | ||
| NPV | 53% (95%CI 45–61) | ||
