Risk of pulmonary embolism after a prior negative computed tomography pulmonary angiogram.
Am J Emerg Med. 2016 Jul 4;
Authors: Hammer MM, Litt HI
CONTEXT: With increasing utilization of computed tomography pulmonary angiography (CTPA) for the diagnosis of pulmonary embolism (PE), many patients undergo repeat CTs.
OBJECTIVE: The aim of this study is to identify the rate of positive subsequent CTPAs after an initial negative CTPA and whether there is a risk-free period after a negative CTPA.
METHODS: We evaluated 318 patients with at least 1 subsequent CTPA after an initial negative CTPA, with 786 total CTPAs. We also evaluated a control group of 200 unselected CTPAs.
RESULTS: The positive rate in the repeat group was 7% at the first repeat CTPA and 10% per-patient within 1000 days. The positive rate in the control group was 9% (P= not significant). No risk-free period was seen, with a positive rate of 5% within 2 weeks after a negative CTPA. The number of prior negative CTPAs showed a trend towards decreasing rate of the subsequent CTPA being positive, but this did not meet statistical significance.
DISCUSSION: There is no risk-free period after an initial negative CTPA, and therefore, patients with clinical suspicion of PE should be rescanned even after a recent negative study. Even patients with multiple negative prior CTPAs have a measurable risk of subsequent PE. Established clinical prediction scoring systems must be used to triage the patients who need CTPAs.
PMID: 27435874 [PubMed - as supplied by publisher]