Age Adjusted D-Dimer for exclusion of Pulmonary Embolism: a retrospective cohort study

D-Dimer (DD) will increase with age and recent studies have shown the upper limit of normal can be raised in those who are low risk and over 50. We studied age adjusted D-dimer (AADD) levels to assess whether pulmonary embolism (PE) could be safely excluded. This study analysed the Emergency Department (ED) Computed Tomographic Pulmonary Angiography (CTPA) requests. There were 756 requests. The parameters studied were; age, DD value, calculated AADD, CT result and Simplified Geneva Score (SGS). The primary outcome was the diagnostic performance of AADD. One hundred and eighty-five patients were included in the final cohort. Twenty-one patients had a negative DD after age adjustment. Of these one had a PE, corresponding to a failure rate of 4.76% (1 in 22). The sensitivity of AADD was 0.96 (95% CI 0.76 to 0.99) and its specificity was 0.12 (95% CI 0.08- 0.19). AADD demonstrated a reduction in false positives with one false negative, giving rise to a failure rate higher than that of other larger studies. Further study is indicated to accurately define the diagnostic characteristics for the Irish context.