Objective: To assess the cost-effectiveness of
spiral CT for the diagnosis of acute pulmonary embolism.
Design: Computer-based cost-effectiveness analysis.
Patients: Simulated cohort of 1,000 patients with suspected
acute pulmonary embolism (PE), with a prevalence of 28.4%, as in the
Prospective Investigation of Pulmonary Embolism Diagnosis study.
Interventions: Using a decision-analysis model, seven
diagnostic strategies were compared, which incorporated combinations of
ventilation-perfusion (V̇/Q̇) scans, duplex ultrasound of the
legs, spiral CT, and conventional pulmonary angiography.
Measurements and results: Expected survival and cost (in
Canadian dollars) at 3 months were estimated. Four of the strategies
yielded poorer survival at higher cost. The three remaining strategies
were as follows: (1) V̇/Q̇ ± leg ultrasound ±
spiral CT, with an expected survival of 953.4 per 1,000 patients and a
cost of $1,391 per patient; (2) V̇/Q̇ ± leg
ultrasound ± pulmonary angiography (the “traditional”
algorithm), with an expected survival of 953.7 per 1,000 patients and a
cost of $1,416 per patient; and (3) spiral CT ± leg ultrasound,
with an expected survival of 958.2 per 1,000 patients and a cost of
$1,751 per patient. The traditional algorithm was then excluded by
extended dominance. The cost per additional life saved was $70,833 for
spiral CT ± leg ultrasound relative to V̇/Q̇ ±
leg ultrasound ± spiral CT.
Spiral CT can replace pulmonary angiography in patients with
nondiagnostic V̇/Q̇ scan and negative leg ultrasound
findings. This approach is likely as effective as—and possibly less
expensive than—the current algorithm for diagnosis of acute PE. When
spiral CT is the initial diagnostic test, followed by leg ultrasound,
expected survival improves but costs are also considerably higher.
These findings were robust to variations in the assumed sensitivity and
specificity of spiral CT.