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Age-adjusted D-dimer testing safely reduces use of PE imaging compared to fixed D-dimer testing

Compared with fixed D-dimer testing, a recent analysis showed an age-adjusted D-dimer testing algorithm safely prevented 5% more patients with suspected pulmonary embolism from being tested using expensive imaging.

“We now know that such a diagnostic algorithm can safely rule out [pulmonary embolism] PE in patients with cancer, [chronic obstructive pulmonary disease] COPD, age 76 years or older, previous [venous thromboembolism] VTE, and delayed presentation, as well as inpatients,” Nick van Es, MD, at the Academic Medical Center in Amsterdam, and colleagues wrote in the Annals of Internal Medicine. “However, the algorithm is less efficient in these subgroups than in the general population presenting with suspected PE.”

Imaging tests are needed to detect PE, the researchers wrote. However, 15% to 25% of presenting patients have PE. As a result, imaging tests, which can be dangerous and costly, are not considered an appropriate first-line test. During the last 2 decades, algorithms have been used to identify which patients with suspected PE can be safely withheld from imaging. Recent studies have shown that age-adjusted algorithms, which take into account patients older than 50 years, can increase the efficiency of fixed D-dimer testing in combination with the Wells rule. However, no individual-patient data meta-analysis has been published to validate this finding. In addition, no meta-analysis has evaluated the overall efficacy of each algorithm nor tested it in at-risk subgroups.

To evaluate and compare the two D-dimer tests in combination with the Wells rule and in at-risk subgroups, the researchers performed a systematic review and individual-patient data meta-analysis of studies between 1988 and 2016. They assessed six prospective studies that used the Wells rule in combination with D-dimer testing to diagnose PE. The studies included 7,268 patients. The subgroups were patients with cancer, COPD, aged 76 years or older, previous VTE, delayed presentation and inpatients.

They found efficiency increased from 28% to 33% from the age-adjusted test to the fixed test for all subgroups. This increase was larger in elderly patients (12%), but less in inpatients (2.6%). The age-adjusted algorithm improved the efficiency for each subgroup. In addition, the failure rate of age-adjusted D-dimer testing was less than 3% in all subgroups.

A diagnostic for PE is considered safe if a failure rate is 3% or less, because even pulmonary angiography cannot detect all cases, the researchers wrote.

“On the basis of this analysis, we recommend using age-adjusted (rather than fixed) D-dimer testing with the Wells rule because it increases efficiency without jeopardizing safety in all studied subgroups,” they wrote. – by Will Offit

Disclosure: Kamphuisen reports grants from the Dutch Thrombosis Foundation during the conduct of the study.