West Virginia University
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Venous duplex ultrasounds (VDUs) may be over-utilized in patients suspected of having deep vein thrombosis (DVT), according to research published in Annals of Vascular Surgery.
The retrospective study indicated that D-dimer tests and the pretest Wells criteria probability (WCP) score could safely exclude DVT.
The researchers therefore believe that consistent use of D-dimer and WCP could reduce the number of unnecessary immediate VDUs, cut costs, and save time.
“Usually, waiting for a venous ultrasound would be a matter of three, four, five hours,” said study author Albeir Mousa, MD, of West Virginia University in Charleston, West Virginia.
“With the D-dimer test, it’s a few minutes, and you’re done.”
For this study, Dr. Mousa and his colleagues reviewed data on 1670 patients who presented to a high-volume tertiary care center with suspected DVT and were referred for VDU. Their average age was 62.1, and 55.7% were female.
The researchers calculated WCP scores for all 1670 patients and divided them into DVT risk groups accordingly—low- (<1), moderate- (1-2), and high-risk (≥3).
The team also divided patients according to D-dimer values—low (0.1-0.59), moderate (0.60-1.2), and high (≥1.3 mg/L FEU).
Results
The researchers found that D-dimer (with an abnormal threshold of ≥0.60 mg/L FEU) identified all patients with DVT (n=183, 11%).
The sensitivity and negative predictive values of D-dimer were both 100%, while specificity was 14.9% and the positive predictive value was 15.9%.
When the researchers used an age-adjusted D-dimer threshold (age x 0.01), the specificity increased from 14.9% to 21.3%, and the positive predictive value increased from 15.9% to 17%.
There were no DVTs among patients with low D-dimer values, but the rate of DVT significantly increased in the moderate (5.9%) and high groups (20.0%; P=0.007).
The rate of DVT increased with increasing WCP as well. The DVT rate was 6.6% in the low WCP group, 14% in the moderate group, and 29.1% in the high group (P<0.001).
The researchers also noted an increase in the rate of DVT across all levels of WCP as D-dimer levels increased.
Based on these findings, the researchers said there were 762 patients who were sent for unnecessary immediate VDUs. This included 685 patients in the low WCP group (<1) who did not undergo D-dimer testing, 51 patients who had moderate D-dimer values, and 26 who had low D-dimer values.
The researchers calculated the potential savings of using D-dimer instead of VDU in these patients, based on US 2016 dollar estimates.
A VDU cost of $1557 per person would mean a total cost of $1,186,434 for 762 patients. A D-dimer cost of $182 per person would mean a total cost of $138,684. So the total potential savings would be $1,047,750.
Dr. Mousa also noted that D-dimer testing is quicker than VDU and requires fewer resources.
“It’s a very simple sample of blood, which is sent to the lab,” he said. “And, usually in 15 or 20 minutes, you have significant information that can help you take good care of the patients. And you can send patients home quicker, with less demand on the hospital staff and the institution, yet increase patient satisfaction.”