CT angiography unnecessary to rule out PE in low-risk patients
MedWire News: Patients should undergo pretest screening for venous thromboembolism (VTE) before undergoing computed tomographic (CT) angiography for pulmonary embolism (PE), US researchers recommend.
PE was confirmed by CT angiography in fewer than 1% of patients without risk factors for VTE, the team reports in the journal Radiology.
“Our study suggests that the frequency of ordering CT angiograms can be markedly reduced with resultant cost-savings and decreased radiation exposure," commented lead author Mark Mamlouk (University of California, Irvine).
The researchers examined medical records for 2003 patients who underwent CT angiography for suspected PE between July 2004 and February 2006 at St Joseph’s Hospital in Phoenix, Arizona, USA.
The records were reviewed for the presence of risk factors for VTE, such as immobility, a hypercoagulable state from inherited disorders or systemic illness, excess estrogen associated with pregnancy, hormone therapy, or use of the contraceptive pill, and history of VTE. Age over 65 years and gender was also noted.
The majority (90.16%) of CT angiograms showed no evidence of PE. Of the 197 patients with PE confirmed by CT angiogram, 6.36% were admitted to the emergency department and 13.46% were inpatients.
Just 0.03% of patients with CT angiogram evidence of PE had no risk factors for VTE. In all, 97.46% of patients with CT angiogram evidence of PE had one or more risk factors for VTE, 48.73% had two risk factors, 19.80% had three, and 11.17% had four or five.
Age over 65 years was the most common risk factor for VTE (69.04%), followed by immobilization (53.81%), male gender (50.76%), malignancy (37.06%), and history of VTE (14.21%).
In contrast, 28.79% of patients with negative CT angiogram results had no risk factors for VTE, rising to 61.96% after excluding age and gender.
Thus, a negative risk factor assessment for VTE was 97.56% sensitive for a negative CT result, with a negative predictive value of 99.05%. These values were improved when combined with a D-dimer test, which had a 100% sensitivity and negative predictive value for PE.
“Unless there is an unusual mitigating circumstance, CT angiography in these settings is likely unnecessary,” the authors conclude.
“This selectivity and triage step should reduce current costs and radiation exposure to patients.”
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By Lynda Williams