D-Dimer Helps Screen for Deep Vein Thrombosis

Laurie Barclay, MD

December 06, 2002

Dec. 6, 2002 — D-dimer may be a useful adjunct to screening for deep vein thrombosis (DVT), according to a report in the November issue of the Journal of Vascular Surgery. The authors suggest that if D-dimer is negative and the difference in calf circumference is less than 2 cm, the patient does not need emergent duplex ultrasound scanning.

"Duplex ultrasonography (DU) is the primary method for diagnosis of DVT but is relatively expensive and not always readily available," write Jason M. Johanning, MD, from the University of Nebraska Medical Center in Omaha, and colleagues from the Geisinger Medical Center in Danville, Pennsylvania. "Attempts to exclude the diagnosis of DVT with D-dimer or clinical criteria independently have been unsuccessful."

In this prospective study, 156 outpatients undergoing DU of the lower extremities for suspected DVT were evaluated using a second-generation rapid quantitative D-dimer and simple clinical parameters. Patients undergoing lower extremity venous ultrasound scan for suspected pulmonary embolism or those already receiving anticoagulants were excluded.

Of 22 patients diagnosed with DVT, 21 had elevated D-dimer levels of at least 0.5 ng/mL, yielding a sensitivity of 95% and negative predictive value of 99%. Although 94% of subjects had symptoms of swelling or pain, 14 (64%) of 22 patients with proximal DVT had symmetric calf swelling of more than 2.0 cm, compared with 22 (16%) of 134 patients without DVT ( P < .003). Multivariate analysis revealed that no single clinical history variable reliably predicted DVT. However, all subjects with proximal DVT had either leg swelling of more than 2 cm or an elevated D-dimer level.

Study limitations include analysis of outpatients only; failure to evaluate every patient with bilateral duplex scans, serial ultrasound scans, or complete calf vein evaluation; no change in routine patient evaluation; and possible bias because this was not a consecutive series of patients.

"A combination of D-dimer and calf circumference provides an easy and effective means of excluding DVT in patients suspected of having proximal DVT," the authors write. "A combination of D-dimer less than 0.5 ng/mL and calf circumference of 2 cm or less reliably excludes DVT in the acute setting and allows for use of DU in a nonemergent setting. Patients with a positive D-dimer or calf circumference of more than 2 cm require emergent DU to exclude DVT."

J Vasc Surg. 2002;36:877-880

Reviewed by Gary D. Vogin, MD

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