Labs commonly report the test as fibrinogen equivalent units (FEUs) with the cutoff at 500 ng/mL and most studies used the FEU values for derivation or validation.  If reported by the lab as a D-dimer unit (DDU) the cutoff is often 230 ng/mL.  2 FEUs equal 1 DDU.<unk>  (years) x 10 ug/L for patients > 50 years of<unk> 
Patient<unk>  75 =<unk>  of 750 ug/L
If using a lab with a cutoff of 230 (DDU assay) then formula is<unk>  x 5
Patient<unk>  75 =<unk>  of 750 ug/L
Age adjusted D-dimer
Modified Wells Score
Thromboelastography 
Bubble study
Cardiac enzymes
Brain natriuretic peptide
Aortic ultrasound
Ankle-brachial index