Conversely, an obstructed or severely reduced blood flow to a pulmonary segment can be caused by focal parenchymal disease or an embolism other than a venous thrombosis. In these instances, the uFPA would be normal; however, V/Q scans may be suggestive of PE. Indeed, there is one patient in this study who had a “high probability of PE” V/Q scan interpretation and normal uFPA concentration (Fig 1). A PA study done within a few hours after V/Q scan was negative for PE. Two other patients had a “moderate probability of PE” V/Q scan pattern, a test result that neither makes nor excludes the diagnosis of PE. These two patients were referred for PA studies (as commonly occurs under such circumstances), which were negative, as were the uFPA tests. Consequently, by using the combination of uFPA and V/Q scans, PE may be excluded noninvasively in more patients than by using either test alone, and, therefore, the need for performing PA may be reduced. antibiotics levaquin
The major limitation of this report is the relatively small number of patients with PE and the large number of excluded patients. This study did not impose a defined diagnostic evaluation algorithm, but rather prospectively included the patients that met definitive criteria. Consequently, the majority of excluded patients had a diagnosis made on the basis of suggestive test results and clinical impression.