The authors must be commended on their elaborate effort to prove the futility of D-dimer testing in postoperative patients. Innumerable studies have been done to try and prove the usefulness of D-dimer testing along with pre-test probability score, all aimed at avoiding expensive imaging.1–3 The study could have been more meaningful if they had clarified the following issues:
The specificity and sensitivity of D-dimer levels vary with the type of test-enzyme-linked immunofluorescence assay (ELFA), microplate enzyme-linked immunosorbent assay (ELISA) or latex quantitative assay; the authors have not mentioned which test type did they use.4
In the historical controls, only 37% patients had deep vein thrombosis (DVT) on or before day 7 after joint replacement surgery. The assessment of D-dimers pre-operatively and on postoperative days 1, 3, 5, 7 and duplex imaging on day 7 would have missed out a major proportion of patients likely to develop DVT (up to 63%). Considering the fact that the authors first presented this work in 2005, follow-up data on these 78 patients, if available, could have made the present publication more meaningful.
The value of day 1 D-dimer in the published abstracts5,6 of their presentations is 3.63 compared to 3.39 in the present article, without any obvious change in any other numbers, probably a typing error in the present article.
D-Dimer should remain as a screening test for proximal DVT and pulmonary embolism for out-patients with low clinical probability of DVT, where it obviates the need for a duplex ultrasound examination. Positive D-dimer, irrespective of its value, has little meaning when the probability of clinical DVT is high.
Footnotes
References
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