Credit: Medical College
of Georgia
A new study shows that, although age-adjusted D-dimer testing produces fewer false-positive results than conventional D-dimer testing, some cases of pulmonary embolism (PE) slip through the cracks.
Researchers compared the two testing methods in patients older than 50 and found that using an age-adjusted D-dimer threshold reduced the need for additional imaging.
Unfortunately, it also had a false-negative rate of 1.5%, failing to catch PE in 4 patients.
Scott Woller, MD, of Intermountain Medical Center in Salt Lake City, Utah, and his colleagues reported these findings in CHEST.
The team conducted this study with the goal of eliminating false-positive D-dimer results and reducing the need for additional imaging, which can be detrimental to older patients.
“A CT scan is most often used to ultimately rule out a pulmonary embolism,” Dr Woller said. “However, it delivers radiation to the patient and contrast dye.”
“Elderly patients are at greater risk for inadvertent harm related to the CT scan, and the contrast dye may also impact kidney function. Plus, the scan adds to the cost of the patient’s care. If we can safely and accurately diagnose the patient’s risk of a pulmonary embolism using [age-adjusted D-dimer], we can eliminate the need for additional imaging tests.”
With this in mind, the researchers evaluated 923 patients older than 50 years of age who presented to the emergency department at Intermountain Medical Center with a suspected PE, a calculated Revised Geneva Score (RGS), and a D-dimer test.
All of the patients underwent CT pulmonary angiography (CTPA), and the researchers compared the false-negative rate of a conventional D-dimer threshold with an age-adjusted D-dimer threshold.
The team found that age-adjusted D-dimer reduced the need for CTPA by 18.3% (95% CI, 15.9%-21.0%), compared to conventional D-dimer.
However, in the 273 patients with a negative age-adjusted D-dimer result and an RGS of 10 or greater, 4 PEs occurred within 90 days. This translates to a false-negative result rate of 1.5% (95% CI, 0.4%-3.7%).
In comparison, the false-negative rate for conventional D-dimer was 0% (95% CI, 0%-2.8%). Among the 104 patients who had a negative test result and an RGS of 10 or greater, there were no PEs within 90 days.
These results suggest an age-adjusted D-dimer threshold does reduce the need for imaging in patients older than 50, the researchers said. They added that this method is probably safe for these patients, but a prospective trial is needed to more thoroughly investigate safety.
