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Risk Factors for Thromboembolism
- Francesco Rodeghiero, MD; and
- Alberto Tosetto, MD
- S. Bortolo Hospital; 36100 Vicenza, Italy (Rodeghiero) S. Bortolo Hospital; 36100 Vicenza, Italy (Tosetto)
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IN RESPONSE:
We thank Dr. Williams for his comment on our test for resistance to activated protein C. As he correctly points out, we measured resistance as originally described by Dahlback in 1993 (1). In fact, our investigation began just a few months before the factor V Leiden mutation was described, and we elected not to change our methods during the study. Dilution of plasma samples with factor V-deficient plasma is an efficient way to identify carriers of the factor V Leiden mutation (2), and many laboratories use this “improved” method to avoid the molecular test. Our findings clearly indicate that resistance to activated protein C is not equivalent to the factor V Leiden mutation. Rather, when the original method is used, a substantial fraction (up to 12%) of the population has a phenotype similar to that of factor V Leiden mutation carriers and has a similarly higher risk for thrombosis. Thus, laboratories relying on the modified activated protein C resistance test (or on molecular diagnosis) could miss some useful information.
Dr. Jay states that our results should have also been adjusted for smoking status. Definite evidence that smoking is an independent risk factor for venous thromboembolism is still lacking. Furthermore, in a previous paper we reported that smokers had a slightly higher response to activated protein C than nonsmokers (3). Assuming that smoking is a risk factor for venous thromboembolism, its effect should result in an underestimation of risk in our cohort. Thus, although we appreciate Dr. Jay's comments, we do not believe that our study results are affected by not controlling for smoking.
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
