Table 3.
Diagnostic performance of the hypodense sign for proven, probable and highly-possible IMD (86 patients) relative to other CT findings
| CT finding | Frequency of sign in 86 patients | Sensitivity(95% CI) | Specificity(95% CI) | Positive LR(95% CI) | Negative LR(95% CI) | Diagnostic odds ratio (95% CI) |
| Halo sign (on HRCT and CTPA) | 67.7% | 0.68 (0.57–0.78) | 0.56 (0.39–0.71) | 1.58 (1.13–2.38) | 0.53 (0.36–0.83) | 2.94 (1.27–6.84) |
| Hypodense sign on HRCT | 23.2% | 0.23 (0.13–0.36) | 1.00 (0.95–1.00) | ∞ (4.33–∞) | 0.77 (0.65–0.87) | ∞ (4.50–∞) |
| Hypodense sign on CTPA | 63.9% | 0.64 (0.52–0.74) | 0.98 (0.87–1.00) | 26.22 (5.00–148.82) | 0.37 (0.27–0.48) | 68.90 (10.11–299) |
| Vessel occlusion sign (on CTPA)a | 97.4% | 0.97 (0.91–0.99) | 0.97 (0.86–0.99) | 37.02 (5.35–256.19) | 0.02 (0.007–0.10) | 1406.00 (123–16009) |
| Vessel occlusion sign (on CTPA)b | 88.4% | 0.88 (0.79–0.94) | 0.97 (0.87–0.99) | 36.23 (5.22–251.50) | 0.12 (0.07–0.21) | 304.00 (37–2460) |
CI, confidence interval; CTPA, CT pulmonary angiography; HRCT, high resolution CT; LR, likelihood ratio; VOS, vessel occlusion sign. ∞, infinity sign, not calculable.
The diagnostic performance of the halosign is the same on unenhanced HRCT and CTPA; the vessel occlusion sign is visible only on enhanced CTPA scan, and the CTPA increases the sensitivity of the hypodense sign respect to HRCT.
aExcluding indeterminate VOS (8/86 of patients who underwent CTPA had not-evaluable results because of coughing, breathing, technical noise or insufficient nodule volume).
bIncluding indeterminate VOS (8/86 of patients who underwent CTPA had not-evaluable results because of coughing, breathing, technical noise or insufficient nodule volume).