J Korean Soc Radiol.  2011 May;64(5):457-463. 10.3348/jksr.2011.64.5.457.

Use of CT Angiography in a Country with Low Pulmonary Embolism Prevalence: Correlation with Clinical Pretest Probability and D-dimer Values

• Lee G
• Jeong YJ
• Kim KI
• Kim CW
• Chung SW
• Kim YD
• Song JW

• KMID: 2040814
• DOI: http://doi.org/10.3348/jksr.2011.64.5.457

Abstract

PURPOSE
To assess the use of CT angiography (CTA) in the diagnostic evaluation of pulmonary thromboembolism (PE) in a country with low PE prevalence and correlate the diagnostic performance of CTA with the clinical pretest probability and D-dimer values.
MATERIALS AND METHODS
The institutional review board approved this retrospective study. The observers reviewed all 660 CTAs and calculated the PE clot burden scores. The pretest probability of PE according to the Wells criteria and D-dimer values were calculated (clinical data were available for 371 of the 660 patients). We correlated the PE positivity rates of CTA and a PE clot burden score with the D-dimer values and pretest probability using Pearson's correlation coefficient.
RESULTS
Of the 371 patients whose clinical data were available, 122 (32.8%) had PEs. None of the patients with both a normal D-dimer value and a low clinical probability had a PE. PE positivity rates of CTA were correlated with clinical pretest probability (r = 0.164, p = 0.002) and D-dimer values (r = 0.361, p < 0.001). PE clot burden scores were correlated with D-dimer values (r = 0.296, p < 0.001).
CONCLUSION
Although PE positivity rates of CTA in a country with low prevalence were higher than those in a country with a higher prevalence, approximately 30% of the yield still represents an overuse of CTA. CTA should be performed after the pretest probability has been assigned and if the result of a D-dimer assay is abnormal.

MeSH Terms

Angiography
Ethics Committees, Research
Fibrin Fibrinogen Degradation Products
Humans
Prevalence
Pulmonary Embolism
Retrospective Studies
Tomography, X-Ray Computed
Fibrin Fibrinogen Degradation Products

Figure

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  Fig. 1 Acute pulmonary thromboembolism in a 31-year-old man with a history of recent lower leg surgery. His serum Ddimer value was 3.44 µg/mL, and he had an intermediate clinical probability of suffering a pulmonary thromboembolism. The pulmonary thromboembolism burden score was 20. The mediastinal window of a contrast-enhanced CT (2.0-mm section thickness) scan obtained at the level of the left inferior pulmonary vein shows multifocal filling defects (arrows) in the segmental arteries of both lungs.

• 

  Fig. 2 Acute pulmonary thromboembolism in a 50-year-old woman with a history of systemic lupus erythematosus. Her serum D-dimer value was normal and she had an intermediate clinical pretest probability of suffering a pulmonary thromboembolism. The pulmonary thromboembolism clot burden score was 1. The mediastinal window of a contrast-enhanced CT (2.0-mm section thickness) scan obtained at the level of the left inferior pulmonary vein shows a filling defect (arrow) in a segmental artery of the left lower lobe.

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