Lung scintigraphy and helical computed tomography for the diagnosis of pulmonary embolism: A meta-analysis

To assess the diagnostic value of lung scintigraphy and helical computed to mography (hCT) in patients with suspected pulmonary embolism (PE), all Engl ish-language articles that described lung scintigraphy and hCT in patients with suspected PE were retrieved. Articles were assessed for strength of me thodology, based on nine a priori-defined criteria. Parameters of diagnosti c accuracy and results of management studies were calculated and evaluated. Lung scintigraphy is diagnostic in approximately 50% of patients with susp ected PE. A normal perfusion scan has a chance of recurrent PE in two of 69 3 patients (0.3%; 95% CI: 0.2-0.4%; fatal in 0.15%). A high-probability lun g scan is correlated with angiographically proven PE in 308 of 350 patients (88%; 95% CI: 84-91%). Pulmonary embolism was proven in 385 of 1529 patien ts (25%; 95% CI: 24-28%) with a nondiagnostic lung scan. Helical CT studies were compared with angiography and lung scintigraphy in 1171 patients, wit h a prevalence of PE of 39%. The sensitivity and specificity of hCT was 283 /320 (88%; 95% CI: 83-91%) and 374/408 (92%; 95% CI:89-94%), respectively. Only one prospective management study using hCT was available. In patients in whom anticoagulants were withheld based on a normal hCT study, recurrent thromboembolic events occurred in six of 109 patients (5.5%; 95% CI: 2-12% ), with one fatality (1% 95% CI: 0.02-4.3%). Lung scintigraphy is evaluated extensively and yields a diagnostic result in 50% of patients. Helical CT has similar positive predictive value to a high-probability lung scan. Howe ver, the exact role of hCT in the management of patients with suspected PE needs to be determined in prospective studies.