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Helical Computed Tomography as a Test for Pulmonary Embolism
- Menno V. Huisman, MD;
- Marco J.L. van Strijen, MD; and
- Peter M.T. Pattynama, MD
- From Leiden University Medical Center, 2300 RC Leiden, the Netherlands; Leyenburg Ziekenhuis, 2545 CH The Hague, the Netherlands; and Erasmus Medical Center Rotterdam, 3000 CA Rotterdam, the Netherlands.
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IN RESPONSE:
Drs. Perrier and Bounameaux draw attention to the relatively low incidence of DVT (0.8%) that we found in patients with normal CT results. They argue that because other investigators have found higher incidences of DVT in similar samples, ultrasonography of the leg veins should still be performed in such patients after normal results on single-slice helical CT. We agree with this view, which in fact reflects the opinion stated in our paper. As we pointed out in the Discussion section, other large-scale studies (different from the ones cited by Drs. Perrier and Bounameaux) have also shown a higher incidence of DVT, ranging from 3.6% to 5.5% (1, 2). This led us to recommend that “it may be prudent to reinforce the finding of a normal helical CT scan with compression ultrasonography on the day of referral to rule out DVT.”
Drs. Perrier and Bounameaux also question the fact that we did not specify the diagnostic criteria used by the radiologists in our study to establish alternative diagnoses. Our study was a management study in a real-life setting. The CT examinations were therefore done within the context of routine clinical patient care (and, of course, the radiologist was aware of all relevant clinical information when reading the CT scan). As a consequence of this study design, the entire spectrum of thorax pathology could have been encountered in our patients. We previously reported on the many unforeseen alternative diagnoses found in patients with suspected pulmonary embolism, including esophageal rupture, aortic dissection, and acute osteoporotic vertebral collapse (3). We felt that limiting the variety of alternative diagnoses beforehand by specifying restrictive diagnostic criteria was illogical, unnecessary, and even inappropriate. Rather than applying exhaustive lists of criteria citing all possible diagnoses from radiology CT textbooks, we chose to use the phrase established criteria of radiologic practice instead. The presence of alternative diagnoses was not used as evidence to rule out pulmonary embolism, as Drs. Perrier and Bounameaux seem to imply. The presence or absence of pulmonary embolism, as we stated in our paper, was determined solely on the basis of the direct CT criteria for pulmonary embolism established by Remy-Jardin and colleagues (4).
In our study, we used helical CT to test consecutive patients with suspected pulmonary embolism. In patients whose CT results were negative for pulmonary embolism but who had an alternative diagnosis, the referring clinician and the radiologist decided together whether the alternative diagnosis could be a plausible cause of signs and symptoms. Using this diagnostic design, we observed a favorably low recurrence rate of venous thromboembolism—1.5%—during 3 months of follow-up. We agree with Drs. Perrier and Bounameaux that because the number of patients in this subcategory was small (n = 130), the confidence limits around this point estimate are still rather wide and that future studies are warranted.
Menno V. Huisman, MD
Leiden University Medical Center; 2300 RC Leiden, the Netherlands
Marco J.L. van Strijen, MD
Leyenburg Ziekenhuis; 2545 CH The Hague, the Netherlands
Peter M.T. Pattynama, MD
Erasmus Medical Center Rotterdam; 3000 CA Rotterdam, the Netherlands
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
- Copyright ©2004 by the American College of Physicians
