Twenty-five prospective cohort studies with more than 7,000 patients were included.
No heterogeneity in the incidence of pulmonary thromboembolism was found among similar diagnostic studies.
All referred patients (19 studies, 4,096 patients).
The strategies associated with low failure rates were: normal results on pulmonary angiography with failure rate 0.8% (upper 95% CI: 2.1%), based on 1 study with 931 patients; normal results on lung scintigraphy with failure rate 0.9% (upper 95% CI: 2.3%), based on 7 studies with 441 patients; and normal D-dimer levels combined with low clinical probability with failure rate 0.2% (upper 95% CI: 0.8%), based on 4 studies with 894 patients.
Second-round tests (20 studies with 3,376 patients).
In patients with a non-diagnostic lung scan, the strategies associated with low failure rates were: normal pulmonary angiography with failure rate 0.0% (upper 95% CI: 3.5%), based on 1 study with 105 patients; and normal serial leg testing for venous thrombosis with failure rate 1.7% (upper 95% CI: 2.8%), based on 3 studies with 779 patients.
In patients with inconclusive D-dimer tests plus clinical probability, the strategies associated with low failure rates were: normal perfusion lung scan with failure rate 0.0% (upper 95% CI: 1.1%), based on 2 studies with 343 patients; and normal results on spiral CT with failure rate 0.0% (upper 95% CI: 3.5%), based on 1 study with 105 patients.
In patients with inconclusive first-round spiral CT and compression ultrasonography, the use of normal lung scintigraphy and/or pulmonary angiography gave low failure rates 0%, (upper 95% CI 4.3%), based on 1 study with 84 patients.
Strategies after two diagnostic rounds (7 studies).
Most of the studies had small sample sizes. Three studies (130 patients) examined the same diagnostic strategy. These found that in patients with elevated D-dimer levels, non-diagnostic lung scans, and moderate to high clinical probability, normal results on compression ultrasonography and pulmonary angiography had low failure rates of 0.8% (upper 95% CI: 4.2).
The results for other combinations of tests were reported in the paper.