Standalone D-dimer, compression ultrasonography a safe strategy to diagnose DVT
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Referring only patients with a positive D-dimer test to undergo compression ultrasonography, regardless of pretest probability, safely simplified the workup of deep vein thrombosis, according to study results published in Blood Advances.
“To our knowledge, this is the first large prospective study to assess the clinical outcomes of a diagnostic strategy using standalone D-dimer,” Synne Fronas, MD, clinical researcher in the department of emergency medicine at Østfold Hospital Trust in Norway, said in a press release. “This method could result in fewer unnecessary ultrasound examinations because not all high-risk patients are referred — only ones with a positive D-dimer test.”
Current guidelines for the diagnostic workup of DVT include a clinical pretest probability assessment, followed by D-dimer testing for those deemed low risk and compression ultrasonography (CUS) for those deemed high risk. Each of these has been widely studied; however, no one strategy has been identified as superior to others.
Fronas and colleagues prospectively analyzed 1,397 patients (median age, 64 years; 55% women) to determine if referral of only those with a positive D-dimer test result for a single whole-leg CUS, regardless of clinical pretest probability, would simplify the workup of DVT without compromising safety.
Researchers evaluated D-dimer with the STA-Liatest D-Di Plus (Stago Diagnostics) assay, and only patients with levels 0.5 g/mL or greater received CUS. They followed patients with a negative D-dimer result or negative CUS for 3 months to assess the venous thromboembolic rate.
Results showed 415 patients (29.7%) had negative D-dimer, 982 (70.3%) had positive D-dimer and 277 (19.8%) were diagnosed with DVT.
Six patients with negative D-dimer or normal CUS were diagnosed with DVT within 3 months, resulting in a failure rate of 0.5% (95% CI, 0.2-1.2). Three of 415 patients with negative D-dimer only were diagnosed with DVT, for a failure rate of 0.7% (95% CI, 0.1-2.1) for D-dimer as a standalone test.
Among the 698 patients with normal CUS at baseline, three were subsequently diagnosed with DVT during the 3-month follow-up, for a failure rate of 0.4% (95% CI, 0.1-1.3) for whole-leg CUS.
Two patients who had negative D-dimer and did not undergo CUS at baseline died during follow-up. Additionally, three patients who had DVT ruled out by normal CUS at baseline died within the 3-month follow-up. None underwent an autopsy, but VTE was determined not to be the cause of death of any of them.
Researchers acknowledged that the monocentric design of the trial may have adversely affected the generalizability of the findings. Because the study population consisted of those referred to the ED with suspected DVT, this approach may not have the same results among a general patient population.
“We believe using D-dimer as a first test is easier and less user-dependent than the traditional clinical prediction model,” Fronas said in the press release. “Overall, this strategy could reduce the cost, time and resources required to diagnose DVT.”
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