| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Westmead Hospital Westmead, New South Wales 2145, Australia
Garg et al. [1] drew the wrong conclusion in their recent study on the validity of helical CT in pulmonary embolism. That their patients had a favorable clinical outcome is of no surprise because Garg et al. had already selected a low-risk group of patients by excluding those with diagnostic lung scans or thrombus on venous sonography. The outcome of group I would have been favorable irrespective of whether the patients underwent helical CT, some other test, or nothing at all. As an aside, it would be interesting to know whether any of the group I patients underwent lung scans, and if so, how the scans were categorized.
In any case, radiologists need to know what proportion of untreated patients with pulmonary embolism (either with a diagnostic lung scan or pulmonary angiography) and negative findings on helical CT have a good clinical outcome. Although these data are available for lung scans [2, 3], this sort of information is unavailable for helical CT.
References
It is unfortunate that Dr. Larcos did not read our article [1] more carefully. In the discussion section on page 1630, we mention that 57 (73.0%) of 78 patients in group I underwent scintigraphy before CT. However, most patients (n = 37) had scintigraphy during a period when the study protocol required ventilation-perfusion scanning of all patients who underwent helical CT for pulmonary embolism assessment. Most of these 57 patients had either an intermediate probability scan or an indeterminate scan for pulmonary embolism (n = 43). The results of scintigraphy in the remaining 14 patients were discordant with clinical findings. Clinicians chose to perform CT to further evaluate suspected pulmonary embolism in all patients. The probability of pulmonary embolism in patients with intermediate probability or indeterminate lung scans ranges from 30% to 50% in various published series [2, 3]. However, in patients with low-probability scintigraphy interpretations and one or more risk factors for pulmonary embolism, the prevalence of pulmonary embolism is reported to be 12% and 21% respectively [3]. We are pleased to clarify that our group I patients had substantially higher risks for pulmonary embolism than the other two groups. Probably, it would not have been wrong if the conclusion of our article read, "a helical CT scan can be effectively used to rule out clinically significant pulmonary emboli in high-risk patients...." However, we assessed the clinical usefulness of negative helical CT findings for pulmonary embolism. The negative predictive value of helical CT for pulmonary embolism may be even better in lower risk patients without comorbid conditions in whom a technically adequate study can be reliably obtained.
In our study, patients who did not undergo lung scanning had abnormal findings on chest radiographs, which prompted clinicians to choose helical CT as the first screening technique. Among patients with angiographically documented pulmonary embolism in one study, only 12% (45/383) of patients had a chest radiograph interpreted as normal [4]. Moreover, the scintigraphy results are often nondiagnostic in the presence of radiographic abnormalities. CT in most cases not only detects the presence of pulmonary embolism (similar to pulmonary angiography) but also reveals and characterizes pleuroparenchymal abnormalities. On the basis of the materials, methods, and results in our study, we drew the correct conclusion.
I agree that the outcome information is unavailable for untreated patients with pulmonary embolism and negative helical CT findings.
References
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
