Diagnosis of pulmonary embolism with CT pulmonary angiography: a systematic review

Abstract

Objective: To appraise the evidence on the diagnostic accuracy of CT pulmonary angiography and the prognostic value of a negative CT pulmonary angiogram in the diagnosis of pulmonary embolism. Methods: Medline, EMBASE, and grey literature were systematically searched by two researchers. Any study which compared CT pulmonary angiography to an acceptable reference standard or prospectively followed up a cohort of patients with a normal CT pulmonary angiogram was included. Study methods were appraised independently by two researchers, and data were extracted independently by three researchers. Results: Thirteen diagnostic and 11 follow up studies were identified. Studies varied in prevalence of pulmonary embolism (19-79%), patient groups, and method quality. Few studies recruited unselected emergency department patients. There was heterogeneity in the analysis of sensitivity (53 to 100%), specificity (79 to 100%), and false negative rate (1.0 to 10.7%). The pooled false negative rate of combined negative CT pulmonary angiography and negative deep vein thrombosis testing was 1.5% (95% CI 1.0 to 1.9%). Conclusion: Diagnostic studies give conflicting results for the diagnostic accuracy of CT pulmonary angiography. Follow up studies show that CT pulmonary angiography can be used in combination with investigation for deep vein thrombosis to exclude pulmonary embolism.T he diagnosis of pulmonary embolism is challenging as symptoms of pulmonary embolism are varied and range from mild, non-specific lethargy or breathlessness, to collapse and cardiac arrest.1-3 Recurrent pulmonary embolism is associated with a case mortality of 26%. 4 Early diagnosis is essential as even patients with minor symptoms are at risk of recurrent pulmonary emboli.The combination of a normal D-dimer concentration and low clinical probability score 5-7 provides a robust screening method, facilitating exclusion of pulmonary embolism without diagnostic imaging. The PIOPED study 8 proposed combining ventilation-perfusion scanning with clinical probability for the safe exclusion and diagnosis in a subset of patients. This strategy does not exclude or diagnose pulmonary embolism in all suspected cases. The gold standard investigation-pulmonary angiography-is invasive and carries a recognised morbidity and mortality. Furthermore, a normal angiogram is associated with a 1.6% incidence of venous thromboembolism in the following year. 10Computed tomographic pulmonary angiography (CT pulmonary angiography) is increasingly used in the diagnosis of pulmonary embolism. CT has the advantage of imaging the entire thorax, facilitating the diagnosis of conditions mistaken for pulmonary embolism, such as pneumonia, aortic dissection, and malignancy.11 UK and US guidelines have planted CT among the basic investigations for pulmonary embolism.12 13 Attempts to evaluate the clinical utility of CT pulmonary angiography have been complicated by rapid advances in CT scanning technology, acceptance that angiography may not be the most appropriate reference standard, and he...

Review of the Evidence on Diagnosis of Deep Venous Thrombosis and Pulmonary Embolism

“…The 9 reviews included 33 primary studies, of which 8 studies were most consistently included across reviews. The newest reviews, 59,[66][67][68] published in 2005 and 2006, included studies published since 2000, which were not included in the earlier reviews. Only 1 review included the study by Winer-Muram, which used multidetector CT. 69 The systematic reviews reported a wide range of summary sensitivities (66%-93%), with only 1 review reporting a summary sensitivity of greater than 90%.…”

“…61,62 Five reviews included only prospective studies. [62][63][64]66,68 The description of search methods was generally the weakest element across systematic reviews (Supplemental Appendix 4, available online at http:// www.annfammed.org/cgi/content/full/5/1/63/ DC1). The 9 reviews included 33 primary studies, of which 8 studies were most consistently included across reviews.…”

“…[60][61][62][63][64][65][66][67][68] All reported either sensitivity and specifi city, or positive and negative likelihood ratios, as the primary indicators of CT performance, but they differed considerably in how the reference standard was defi ned. Four reviews included only studies in which conventional pulmonary arteriography was the reference standard, 60,63,66,67 while the other reviews expanded the defi nition of a reference standard to include ventilation-perfusion scintigraphy 64,65,68 or overall clinical assessment. 61,62 Five reviews included only prospective studies.…”

“…We identifi ed 10 systematic reviews summarizing the accuracy of helical CT for the diagnosis of pulmonary embolism, [59][60][61][62][63][64][65][66][67][68] and excluded 1 study 59 for unclear study inclusion criteria (Table 4). [60][61][62][63][64][65][66][67][68] All reported either sensitivity and specifi city, or positive and negative likelihood ratios, as the primary indicators of CT performance, but they differed considerably in how the reference standard was defi ned.…”

Gradient-based enhancement of tubular structures in medical images

“…Imaging and analyzing these structures is important for diagnostic purposes. As an example, computer tomography angiography (CTA) is now a standard clinical tool for diagnosing coronary artery diseases (Weustink and de Feyter, 2011;Marwan et al, 2014) and pulmonary embolism (Mos et al, 2009;Hogg et al, 2006). Magnetic resonance angiography (MRA) is used clinically for imaging the cerebral vessels (Parker et al, 1998) as well as the renal and peripheral arteries (Dong et al, 1999;Prince et al, 1999).…”