We use D-dimer in patients with a low probability of a pulmonary embolism, to rule out the condition and thus avoid imaging. The level of D-dimer rises with many conditions and also with age, thereby reducing it’s specificity for this condition. In a retrospective cohort study of D-dimer cut-offs, Ackerly et al(1) compared three proposals for D-dimer adjusted cut-offs in patients over 50 years of age.
Proposal 1
age (years) x 10 (2)
Proposal 2
age (years) x 16 (3)
Proposal 3 (4)
Decade specific cut-offs
-< 60yo 500 mcg/L
-61-70 600 mcg/L
-71-80 700 mcg/L
Results are shown below:
It is important to know that the decade specific and age x 10 PE’s that were missed were sub-segmental. half of the age x 16 were sub-segmental. It comes back to the question of what is an acceptable cut-off? How many are you prepared to miss?
I agree with the authors that the age x 10 is easy to remember and apply.
More to come on this.
References
1 Ackerly I et al. Which age adjusted D-dimer cut-off performs best? EMA Vol 29, Issue 5, October 2017
2 Flores J et al. Clinical usefulness and safety of an age-adjusted D-Dimer cut-off levels to exclude pulmonary embolism: a retrospective analysis. Intern Emerg Med 2016;11:69-75
3 Verma N et al. Age-adjusted D-dimer cut-offs to diagnose thromboembolic events: validation in an emergency department. Med Klin Intensivmed Norfmed. 2014;109:121-128
4 Gupta A et al. Assessing a 2 D-dimer age-adjustment strategies to optimise computed tomographic use in ED evaluation of pulmonary embolism. Am J. Emerg. Med. 2014;32:1499-1502.
