Accuracy of CT in the Diagnosis of Pulmonary Embolism
Accuracy of CT in the Diagnosis of Pulmonary Embolism
Objective: We sought to summarize systematically the published evidence describing the accuracy of contrast-enhanced helical CT for diagnosing pulmonary embolism.
Materials and Methods: We selected all systematic reviews published before December 2003 that evaluated the accuracy of CT angiography for the diagnosis of pulmonary embolism. We also selected all prospective studies from the same time period in the primary literature in which all subjects underwent both CT and conventional angiography, the latter being considered the reference standard. Articles were identified through a computerized MEDLINE search and by other means. The quality and content of each article were evaluated independently by pairs of researchers.
Results: Six systematic reviews and eight primary studies were selected. The combined sensitivities of CT for detecting pulmonary embolism ranged from 66% to 93% across the systematic reviews and the combined specificities ranged from 89% to 97%. Only one of the reviews reported a combined sensitivity of greater than 90%. Among the eight primary studies, the sensitivities ranged from 45% to 100% and specificities ranged from 78% to 100%. Only three of the eight primary studies reported a sensitivity greater than 90%. None of the primary studies used scanners with four or more detectors.
Conclusion: A systematic literature review revealed a wide range of reported sensitivities, only a minority of which exceeded 90%. Pooled estimates of sensitivity and specificity reported by systematic literature reviews should be interpreted with caution because of potential selection bias and heterogeneity in the reviewed studies. Accuracy studies of recent generations of MDCT scanners are not yet available despite the current dissemination of this technology.
Imaging is an important component in the diagnostic evaluation of patients in whom pulmonary embolism is suspected. Pulmonary arteriography is considered the reference standard test for the diagnosis of pulmonary embolism, but the examination is accompanied by the discomfort, expense, and risk of serious complications associated with an invasive procedure. Ventilation–perfusion scintigraphy has been widely used in the initial evaluation for pulmonary embolism, but the usefulness of this test is limited by a substantial proportion of examinations with indeterminate results and the possibility that pulmonary embolism may be present despite a scan with results that indicate a low probability of pulmonary embolism.
With the advent of high-speed helical scanners in the early 1990s, it became possible to examine the pulmonary arteries for emboli using CT. The advantages of helical CT include rapid examination time, widespread availability in emergency clinical settings, safety because of noninvasiveness, low cost compared with conventional pulmonary arteriography, and the concurrent examination of the lung parenchyma. Helical scanners have since become widely available, and examination of the pulmonary arteries on helical CT has become a routine practice. The recent generation of MDCT scanners provides increasingly detailed images of the pulmonary vasculature and presumably have even greater diagnostic accuracy. Given the high reported accuracy of helical CT, it is reasonable to consider whether that technique can replace traditional imaging techniques for detecting pulmonary embolism (i.e., ventilation–perfusion scintigraphy and pulmonary arteriography by catheterization).
Despite the increasing use of contrast-enhanced CT for the detection of pulmonary embolism, the reported accuracy of this test varies among published reports, with some of the most recent studies reporting sensitivities of approximately 50% Because accuracy is a key consideration in the decision to use diagnostic tests, we conducted a systematic literature review to summarize the best available evidence concerning the accuracy of CT angiography for the diagnosis of pulmonary embolism. Our examination of the literature included stringent methodologic criteria for selecting articles to review that we expected would improve the reliability of our summary of the evidence regarding the accuracy of CT compared with the accuracy reported in previous reviews. In our systematic review of the literature, we focused on sensitivity and specificity as the indicators of diagnostic accuracy, because these indicators are most commonly reported in the literature.
Objective: We sought to summarize systematically the published evidence describing the accuracy of contrast-enhanced helical CT for diagnosing pulmonary embolism.
Materials and Methods: We selected all systematic reviews published before December 2003 that evaluated the accuracy of CT angiography for the diagnosis of pulmonary embolism. We also selected all prospective studies from the same time period in the primary literature in which all subjects underwent both CT and conventional angiography, the latter being considered the reference standard. Articles were identified through a computerized MEDLINE search and by other means. The quality and content of each article were evaluated independently by pairs of researchers.
Results: Six systematic reviews and eight primary studies were selected. The combined sensitivities of CT for detecting pulmonary embolism ranged from 66% to 93% across the systematic reviews and the combined specificities ranged from 89% to 97%. Only one of the reviews reported a combined sensitivity of greater than 90%. Among the eight primary studies, the sensitivities ranged from 45% to 100% and specificities ranged from 78% to 100%. Only three of the eight primary studies reported a sensitivity greater than 90%. None of the primary studies used scanners with four or more detectors.
Conclusion: A systematic literature review revealed a wide range of reported sensitivities, only a minority of which exceeded 90%. Pooled estimates of sensitivity and specificity reported by systematic literature reviews should be interpreted with caution because of potential selection bias and heterogeneity in the reviewed studies. Accuracy studies of recent generations of MDCT scanners are not yet available despite the current dissemination of this technology.
Imaging is an important component in the diagnostic evaluation of patients in whom pulmonary embolism is suspected. Pulmonary arteriography is considered the reference standard test for the diagnosis of pulmonary embolism, but the examination is accompanied by the discomfort, expense, and risk of serious complications associated with an invasive procedure. Ventilation–perfusion scintigraphy has been widely used in the initial evaluation for pulmonary embolism, but the usefulness of this test is limited by a substantial proportion of examinations with indeterminate results and the possibility that pulmonary embolism may be present despite a scan with results that indicate a low probability of pulmonary embolism.
With the advent of high-speed helical scanners in the early 1990s, it became possible to examine the pulmonary arteries for emboli using CT. The advantages of helical CT include rapid examination time, widespread availability in emergency clinical settings, safety because of noninvasiveness, low cost compared with conventional pulmonary arteriography, and the concurrent examination of the lung parenchyma. Helical scanners have since become widely available, and examination of the pulmonary arteries on helical CT has become a routine practice. The recent generation of MDCT scanners provides increasingly detailed images of the pulmonary vasculature and presumably have even greater diagnostic accuracy. Given the high reported accuracy of helical CT, it is reasonable to consider whether that technique can replace traditional imaging techniques for detecting pulmonary embolism (i.e., ventilation–perfusion scintigraphy and pulmonary arteriography by catheterization).
Despite the increasing use of contrast-enhanced CT for the detection of pulmonary embolism, the reported accuracy of this test varies among published reports, with some of the most recent studies reporting sensitivities of approximately 50% Because accuracy is a key consideration in the decision to use diagnostic tests, we conducted a systematic literature review to summarize the best available evidence concerning the accuracy of CT angiography for the diagnosis of pulmonary embolism. Our examination of the literature included stringent methodologic criteria for selecting articles to review that we expected would improve the reliability of our summary of the evidence regarding the accuracy of CT compared with the accuracy reported in previous reviews. In our systematic review of the literature, we focused on sensitivity and specificity as the indicators of diagnostic accuracy, because these indicators are most commonly reported in the literature.
Source...