Application of age-adjusted D-dimer threshold for exclusion thromboembolism (PTE) in older patients: a retrospective study.

BACKGROUND: The D-dimer assay's ability to exclude pulmonary thromboembolism (PTE) falls with age.1,2 Douma et al. have proposed an age-adjusted D-dimer threshold ([threshold, µg/l] = [age, years] x 10) for patients aged >50 years with low clinical risk of PTE.3 We retrospectively applied this threshold to patients who underwent computer tomographic pulmonary angiogram (CTPA) for suspected PTE during a 13 month period at a busy District General Hospital. Of the 423 patients >50 years old who underwent CTPA, 22 (5.2%) had D-dimer concentrations higher than the traditional threshold but lower than the age-adjust threshold, none of whom had evidence of PTE on CTPA. This suggests that use of the age-adjusted D-dimer threshold may reduce necessity for CTPA concept patients aged >50 years.