Value of the ventilation/perfusion scan in acute pulmonary embolism: results of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED)

Article Abstract:

Ventilation/perfusion (V/Q) scanning of the lungs combines two techniques, which provides increased sensitivity and diagnostic capability. This test has been examined for its usefulness in detecting pulmonary embolism (obstruction of the pulmonary artery) in a retrospective random sampling of 933 patients. The study was performed by the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED), under the sponsorship of the National Heart, Lung, and Blood Institute. Other diagnostic tests were performed; 941 of the subjects were tested with scintigraphy, and 755 underwent pulmonary angiography. Abnormal results of the V/Q lung scans were categorized as high, intermediate (indeterminate), or low probability for pulmonary embolism; 98 percent of the patients with pulmonary embolism fell into one of these categories. It was concluded that the sensitivity of the test was high, and may serve as a preliminary screening test for the condition. Eighty-eight percent of the patients with high-probability V/Q scans and angiograms that indicated pulmonary embolism (102 out of 116 patients) were positively diagnosed with pulmonary embolism. However, this test lacked sensitivity, and 59 percent of the patients with pulmonary embolisms were not detected. The PIOPED drew several conclusions from the results of the data. It appears that patients who test positive for pulmonary embolism (high-probability) on the V/Q scan most likely have this condition, but, overall, not all patients with pulmonary embolisms are detected. V/Q scanning for pulmonary embolism in combination with other diagnostic tests and clinical assessment provides an accurate diagnosis for a limited number of patients. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Ventilation/perfusion scan in pulmonary embolism: 'the emperor is incompletely attired.' (editorial)

Article Abstract:

An article appearing in the May 23/30, 1990 issue of the Journal of the American Medical Association presents the results of an investigation into the efficacy of ventilation/perfusion (V/Q) lung scans in detecting pulmonary embolism (obstruction of the pulmonary artery). This study was well done and focused on an area in which there is much need for more knowledge. Pulmonary embolisms are notoriously difficult to diagnose; one study performed in the early 1970s showed correct diagnosis at autopsy in only one third of the cases examined. This Prospective Investigation of Pulmonary Embolism study provides some new information on the capabilities of V/Q lung scan in diagnosis. Its high sensitivity (98 percent), meaning that almost all patients with pulmonary embolisms were detected, was offset by its low specificity. The results also question the notion that all patients with normal or close to normal scans do not have a pulmonary embolism; four percent of the subjects testing in this range were found to have an embolism. An algorithm is provided which utilizes data provided from this study, as well as the results of other studies on noninvasive methods of diagnosing pulmonary embolism. Recent advances in the diagnosis of deep venous thrombi, a condition that often precedes pulmonary embolism, provide additional noninvasive methods of detection. The results of V/Q scanning alone do not provide conclusive evidence, but require additional tests for definitive diagnosis. If indicated, a pulmonary angiogram, a more invasive but more accurate assessment, should be performed. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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Clinical validity of a negative computed tomography scan in patients with suspected pulmonary embolism

Article Abstract:

A study is conducted to review studies that used a computed tomography (CT)-based approach to rule out a diagnosis of pulmonary embolism. The conclusion states that the clinical validity of using a CT scan to rule out pulmonary embolism is similar to that reported for conventional pulmonary angiography.

United States, Usage, CT imaging, CAT scans

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