Optimal Strategies for the Diagnosis of Acute Pulmonary Embolism: A Health Technology Assessment — Project Protocol
CADTH Optimal Use Report, No. 6.3a
Of the total population of patients who are evaluated for suspected PE, few are confirmed to have the condition, indicating a low diagnostic yield of current evaluation methods. Studies report a range of values for the diagnostic yield of CTPA, ranging from less than 5% to 30%, depending on the clinical characteristics of the patient pool, and use of risk stratification strategies. False-positive test results, which, depending on pretest probability, can occur in approximately 10% to 42% of patients who undergo CT scanning, can lead to unnecessary anticoagulation therapy, which carries substantial risk of adverse effects including hemorrhage (occasionally devastating or fatal), interactions with other medications, inconvenience in terms of attendance for repeated blood tests (possibly requiring time off work), implications for future dental and medical procedures, and costs (both to the patient and society). False-negative CT results, which also occur at high frequency (e.g., 1% to 11%), can lead to bypass of necessary treatment, complications, and death. The uncertain benefit of increased testing and the significant expense of PE could suggest that current CT utilization patterns for the diagnosis of PE are not cost-effective. This is reflected in the increased diagnosis of mild PEs, which, if treated, may increase costs and possible harms, and may not reduce mortality. In light of these concerns, it is important to assess whether there are other cost-effective and safe alternatives.
The optimal diagnostic strategy for suspected PE among experts remains controversial, and it can differ based on factors related to the health care setting (i.e., urban, rural, or remote) that may impact access to imaging. The optimal diagnostic strategy would, in theory, be one that has high diagnostic accuracy and clinical utility, at an acceptable cost. However, issues of access may also influence what is considered optimal for different populations. For instance, provision of timely diagnosis may be less feasible in rural and remote facilities due to lack of access to certain testing and imaging modalities and specialist expertise, as well as geographical barriers to care. Inability to access optimal diagnostic testing in a timely manner could increase the risk for missed diagnoses, as well as unnecessary anticoagulation due to either false-positives or long wait times to receive assessment. Patient safety concerns associated with exposure to radiation and contrast media that accompanies several imaging studies also disproportionately affect specific patient groups, including pregnant women, and young women for whom the risk of breast cancer associated with radiation is higher.
Addendum with Ethics Review added October 28, 2016
Suggested citation:
Optimal strategies for the diagnosis of acute pulmonary embolism: a health technology assessment – project protocol. Ottawa: CADTH; 2016 Sep. (CADTH optimal use report; vol.6, no.3a)
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