Diagnostic efficacy of perfusion scans interpreted by PISA-PED criteria for pulmonary embolism: comparison with CTPA

Objective: To compare the diagnostic efficiency of lung perfusion scans in PE interpreted by prospective investigative study of PE diagnosis (PISA-PED) criteria with contrast-enhanced multislice spiral CT pulmonary angiography (CTPA). Methods: One hundred and four consecutive patients with suspected PE were enrolled. All patients underwent lung perfusion scans, CTPA and chest radiography. Lung perfusion scans were interpreted by PISA-PED criteria. Final diagnosis was confirmed using a composite reference test. Kappa test was used to analyze the degree of agreement between the multimodality images. The differences between the multimodality images were tested for significance using nonparametric test or χ²-test. Results: PE was finally diagnosed in 55 of the 104 patients. After excluding three patients (2.9%) with non-diagnostic CTPA from analysis, the sensitivity,specificity, positive predictive value and negative predictive value were 92.6% (50/54), 83.0% (39/47), 86.2% (50/58), 90.7% (39/43) respectively for lung perfusion scans, and 96.3% (52/54 ), 93.6% (44/47), 94.5% (52/55), 95.7% (44/46) respectively for CTPA. The agreement rate between the two modalities was 89.1% (90/101); Kappa=0.78, P<0.05). In the segment-based analysis, a total of 1664 segments were evaluated. The agreement rate between lung perfusion scans and CTPA was 79.7% (1327/1664; Kappa=0.58, P <0.05). Conclusions: Lung perfusion scans interpreted by PISA-PED criteria can provide diagnostic accuracy comparable to CTPA, and the two modalities both show high efficacy in diagnosing PE. The agreement between lung perfusion scans and CTPA was intermediate on a segment-by-segment basis. (authors)