Table 3. Overview of LRs and CXR results in two groups; all patients and patients in whom CTPA was indicated according to the YEARS algorithm.
| All patients ( n = 1,473) | Patients in whom CTPA was indicated according to the YEARS algorithm ( n = 763) |
|||
|---|---|---|---|---|
| Results CXR | Positive LR (95% CI) | Negative LR (95% CI) | Positive LR (95% CI) | Negative LR (95% CI) |
| Normal CXR | 0.86 (0.78–0.96) | 1.4 (1.1–1.7) | 1.1 (0.95–1.2) | 0.89 (0.73–1.1) |
| Pleural effusion | 1.1 (0.66–2.0) | 0.99 (0.95–1.0) | 0.58 (0.33–1.0) | 1.1 (1.0–1.1) |
| Consolidation | 1.8 (1.4–2.4) | 0.88 (0.82–0.95) | 1.4 (0.99–1.8) | 0.93 (0.86–1.0) |
| Malignancy/mass | 0.93 (0.40–2.2) | 1.0 (0.98–1.0) | 0.51 (0.22–1.2) | 1.0 (1.0–1.1) |
| Congestive heart failure | 0.98 (0.45–2.2) | 1.0 (0.97–1.0) | 0.67 (0.29–1.5) | 1.0 (0.99–1.1) |
| Pneumothorax | 0.00 | 1.0 (0.99–1.0) | n.a. | n.a. |
| (Rib) fracture | 0.00 | 1.0 (0.99–1.0) | 0.00 | 1.0 (0.99–1.0) |
| Atelectasis | 0.49 (0.06–3.8) | 1.0 (0.99–1.0) | 0.37 (0.05–3.0) | 1.0 (0.99–1.0) |
Abbreviations: CI, confidence interval; CTPA, computed tomography pulmonary angiography; CXR, chest X-ray; LR, likelihood ratio; n.a., not applicable; PE, pulmonary embolism.
Example: Assuming that the pretest probability of PE is 28% in a certain patient with suspected PE and an indication for CTPA according to YEARS, the posttest probability of PE in case of a normal CXR result would be 28% × 1.1 = 31%. The posttest probability of PE in this patient with any abnormality on CXR would be 28% × 0.89 = 25%.