We've discussed before the use of age-adjusted d-dimer
cut-offs in the exclusion of PE. A recently published retrospective study
found that 4/273 (1.5%) of patients who had a negative age adjusted d dimer had a PE within 30 days, although only 2 of these actually had a PE at the time of presentation. The ages of those patients and their D dimers were as follows: age 92 – d dimer 872 ng/mL (note: a different unit to our local lab reporting), age 75 – d dimer 715.
So there may be a minimally increased risk of missing a PE by using an age adjusted cut off. If you uncomfortable with that, you might want to consider using a cut off of 700 for all patients > 70years of age – but will need to accept you will be investigating more patients.