Clinical QuickieCardiac
D-dimer
D-dimer is a rule-out tool, not a rule-in test.
Start with pretest probability
D-dimer is most useful when PE/DVT probability is low or intermediate. High pretest probability should not be 'rescued' by a negative-looking shortcut.
A positive result is nonspecific
Age, pregnancy, hospitalization, infection, inflammation, malignancy, surgery and thrombosis can all elevate D-dimer.
Use age adjustment when appropriate
In older adults, age-adjusted thresholds can improve specificity while preserving the intended rule-out strategy when used in the correct clinical pathway.
Imaging answers a different question
A positive D-dimer does not diagnose PE. It tells you the rule-out pathway did not end there and further evaluation may be needed.
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