PURPOSE: In our institution we have noted a recent substantial rise in the use of CT pulmonary angiography (CTPA) in the evaluation of atypical chest pain and other syndromes which could be caused by Pulmonary Emboli (PTE) but usually are not. Since there are good prediction rules (e.g. the Wells rules) which can quantitate the clinical risk of PTE, it seems that some of this definitive testing may be avoidable. The incidence of significant contrast reactions, combining anaphylactic/anaphylactoid and renal impairment is about 3%. We thus determined to assess the validity of definitive testing for Pulmonary Embolism in the setting of relatively low pretest probability settings.
METHODS: Retrospective review of Radiology records and patient charts of 100% of patients assessed with CT Pulmonary Angiography for suspected PTE during a 4 month period in this institution.
RESULTS: Of 100 CTPAs performed for suspected PTE, 3 showed evidence of PTE. One non-angiographic CT with contrast demonstrated PTE, but this was an incidental finding during the evaluation of known metastatic lung carcinoma. One of the CTPAs reporting PTE proved on further evaluation to be a false positive. Of the 100 patients, 49 had Wells scores of 0, 3 of 1 and 32 of 1.5. Thus, 84% of the patients had scores indicating a low probability of PTE, and none of these had an embolus. The 2 cases of PTE both had very high Wells scores of 8.5. One had known metestatic cancer and the other presented with hemoptysis 2 weeks after pelvic surgery, both classical presentations and settings for PTE.
CONCLUSION: Performance of CTPA without formal pretest probability stratification in all patients with syndromes whose differential diagnosis includes PTE can result in a rate of disease detection which is approximately equal to the occurance rate of significant complications of the test, itself.
CLINICAL IMPLICATIONS: In the setting of suspected PTE, pretest probability should be formally determined and utilized in the decision to proceed to definitive testing with CTPA.
DISCLOSURE: William Marino, No Financial Disclosure Information; No Product/Research Disclosure Information