Background: Spiral computed tomographic pulmonary angiography (CTPA) is increasingly being used in the evaluation of patients with clinically suspected pulmonary embolism (PE). However, CTPA as a definitive diagnostic test may be limited by inadequate sensitivity, especially in instances of isolated subsegmental emboli.
Purpose: To assess the safety of withholding anticoagulation in patients with suspected PE and negative results on CTPA.
Data Sources: All relevant studies identified in MEDLINE (1966 to March 2004) and EMBASE (1974 to 2004) and in bibliographies of key articles. The search was not limited to the English language.
Study Selection: The authors selected all published studies that used CTPA to evaluate suspected PE and reported at least 3 months of follow-up in patients not receiving anticoagulation on the basis of a negative CTPA result.
Data Extraction: Two reviewers independently rated study quality on the basis of predetermined criteria. Data were extracted on participants, CTPA technique, diagnostic studies performed, prevalence of PE, number of patients with negative or indeterminate CTPA results who were followed, and subsequent rates of venous thromboembolism and fatal PE.
Data Synthesis: Twenty-three studies reported on 4657 patients with negative CTPA results who did not receive anticoagulation. The 3-month rate of subsequent venous thromboembolic events was 1.4% (95% CI, 1.1% to 1.8%), and the 3-month rate of fatal PE was 0.51% (CI, 0.33% to 0.76%).
Limitations: The CTPA technology used varied across studies and was not applied uniformly in the same step of diagnostic algorithms. Only 1 study used CTPA as the sole diagnostic test.
Conclusion: The rate of subsequent venous thromboembolism after negative results on CTPA is similar to that seen after negative results on conventional pulmonary angiography. It appears to be safe to withhold anticoagulation after negative CTPA results.