I do not know who formulated this, but I would like to thank them. I got this off the internet.
Coughing up blood
Lower extremity swelling
Oxygen saturation < 94 % in room air
Tachycardia-HR of > 100
Surgery/trauma in the preceding 4 weeks
If no to all, a patient with low risk for PE as per Well’s criteria does not need D Dimer.