Better Testing Methods for Pulmonary Embolism

Adjusting the value of d-dimer test according to patients’ ages is an effective method to determine patients with pulmonary embolism (PE), according to findings published in the journal CHEST.

Researchers from the Intermountain Medical Center in Salt Lake City, Utah reported the outcomes of 923 patients aged 50 years and older in order to assess the safety of using age adjusted d-dimer threshold in the workup of patients with suspected PE. The patients involved in the study were suspected PE patients and the researchers calculated Revised Geneva Score (RGS) and a d-dimer test. The patients were administered CT pulmonary angiography (CTPA).

Researchers compared the false negative rate for PE of a conventional d-dimer threshold with an age adjusted d-dimer threshold to determine the proportion of patients for whom an age adjusted d-dimer threshold would eliminate the need for CTPA.

For the 104 patients found with a negative conventional d-dimer test result and an RGS ≤ 10, no PE was observed within 90 days. This result showed a false negative response of zero percent. The researchers found 4 PEs among 273 patients with a negative age adjusted d-dimer result and an RGS ≤ 10. There was an 18.3 percent reduction in the proportion of patients aged > 50 years who would warrant CTPA by using an age adjusted d-dimer threshold compared with a conventional d-dimer threshold.

“Use of an age-adjusted d-dimer threshold reduces imaging among patients aged > 50 years with an RGS ≤ 10,” the authors concluded. “Although the adoption of an age adjusted d-dimer threshold is probably safe, the confidence intervals surrounding the additional 1.5 percent of PEs missed necessitate prospective study before this practice can be adopted into routine clinical care.”

The normal cutoff used to identify a normal d-dimer value is 500, but this new research supports evidence that the cutoff rate should be adjusted once a patient reaches the age of 50 years or older. Much of this research suggests the patient’s age should be multiplied by 10; for example, a 72 year old patient would have a normal d-dimer value of less than 720.

“A CT scan is most often used to ultimately rule out a pulmonary embolism, however it delivers radiation to the patient and contrast dye,” lead author Scott Woller, MD, co-director of Intermountain Medical Center’s Thrombosis Program, said in a press release. “Elderly patients are at greater risk for inadvertent harm related to the CT scan, and the contrast dye may also impact kidneys 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 this sliding d-dimer scale, we can eliminate the need for additional imaging tests.”