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Won't it be the normal expectant result.?
Submit responseDear Sir, I read the article on the evaluation of D-Dimer in the diagnosis of pulmonary embolism with great enthusiasm. There Kearon C et al(1) have tried to emphasize the relative less importance of performing additional investigations in patients who are suspected to have pulmonary embolism with a negative D -Dimer test. The idea is of course brilliant and would save valuable resources and manpower which can be utilized to needy patients.
There they have randomly allocated 456 patients out of 1126 who were negative for D- dimer test into a low probability group and moderate or high probability group. Their control intervention for the low probability group was ventilation perfusion lung scan followed by ultrasonography of the proximal deep veins of the legs. The control intervention for the moderate or high probability group was ultrasonography of the proximal deep veins of the legs. Then they have looked for the prevalence of pulmonary embolism in low probability group and moderate or high probability group with additional diagnostic testing and without additional diagnostic testing. Then they have concluded that in patients with a low probability of pulmonary embolism who have negative D-Dimer results ,additional diagnostic testing can be withheld.
But according to Roy PM et al.(2)in patients with a high pretest probability, ventilation perfusion lung scan ,spiral computed tomography and ultrasonography of leg veins have a greater than 85% of posttest probability of pulmonary embolism. In patients with a low probability of pulmonary embolism, these tests have only 5% post test probability of pulmonary embolism. Not only the D-Dimer test but also magnetic resonance angiography ,quantitative latex D-Dimer test can only exclude pulmonary embolism in patients with a low probability of pulmonary embolism only. Helical CT appears to a rapid and non invasive diagnostic test in patients with moderate to high risk of pulmonary embolism.(3)So the findings by Kearon C et al seems to be the proven expected in the diagnosis of pulmonary embolism.
References (1)Clive Kearon,Ginberg JS,Douketis J et al.An evaluation of D-Dimer in the diagnosis of pulmonary embolism. Annals of Internal Medicine. 2006 Jun 6;144(11):812-21.
(2)Roy PM,Colombert I,Durieux P et al.Systemic review and meta analysis of strategies for the diagnosis of suspected pulmonary embolism.BMJ 2005 Jul 30;331(7511):259.
(3)Rahimtoola A,Berjin JD.Acute pulmonary embolism: an update of diagnosis and management.Curr Probl Cardiol 2005 Feb;30(2):61-114.
Conflict of Interest:
None declared
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D-dimer Should Be Viewed with Caution
Submit responseIn their prospective study evaluating D-dimer as a tool to rule-out pulmonary embolism (PE), Kearon et al1 described as a primary finding the low incidence of PE when D-dimer is used as a stand-alone test to rule-out disease among patients with low clinical probability. We agree with the authors that it is essential for physicians to interpret the real value of D-dimer as a test to diagnose VTE and we also applaud their efforts towards clarifying its place. Although interesting, we believe that the conclusions of the authors should be viewed with caution based on the following observations of their methodology:
First, all randomized patients with negative D-dimer and a non- diagnostic V/Q scan should be included in the final analysis. The three cases of venous thromboembolism (VTE) excluded due to deviations in the protocol (refer to figure 2 of the article) should count as new occurrences of VTE in the cohort. If as the conclusion suggests no additional tests were conducted, these new enrollment cases would likely not have been discovered. Due to the fact that these new cases of VTE occurred after randomization and after additional diagnostic testing, it is only reasonable to include them in the final analysis. Thus, there should be 4 VTE cases in the additional testing group, which would result in a prevalence of 2.2%. Although including these initially excluded VTE cases does not confirm a significant difference between the two groups (no additional versus additional testing), it does however increase the prevalence of VTE to be higher than the a priori 1% expected by the authors (which was later readjusted to be 2.1% after restarting the study). The higher, but expected, prevalence of VTE in the additional testing group is troublesome. The prevalence should be similar between the no additional versus additional testing groups. Thus, readers should be cautioned about withholding additional diagnostic testing until more convincing evidence is presented.
Second, even with the use of the most sensitive D-dimer assay (ELISA); this test has demonstrated to only increase the rate of subsequent testing to rule-out PE without any benefits regarding its diagnostic capability.2 The failure of D-dimer to rule-out disease has been also reported by others, and in our opinion the authors of this study failed to explain this noteworthy dissimilarity between their results and previous publications.
References:
1. Kearon C, Ginsberg JS, Douketis J, Turpie AG, Bates SM, Lee AY, Crowther MA, Weitz JI, Brill-Edwards P, Wells P, Anderson DR, Kovacs MJ, Linkins LA, Julian JA, Bonilla LR, Gent M; Canadian Pulmonary Embolism Diagnosis Study (CANPEDS) Group. An evaluation of D-dimer in the diagnosis of pulmonary embolism: a randomized trial. Ann Intern Med. 2006; 6:812-21. (PMID: 16754923)
2. Ray P, Bellick B, Birolleau S, Marx JS, Arock. Referent D-dimer enzyme-linked immunosorbent assay testing is of limited value in the exclusion of thromboembolic disease: result of a practical study in an ED. Am J Emerg Med. 2006; 24:313-8. (PMID: 16635704)
Conflict of Interest:
None declared