A couple weeks back I posted regarding a study where even intermediate- and high-risk patients with suspected PE had negative CTA in the presence of low d-Dimers. Based on that post, I’ve put together a rough decision tree encapsulating how I (currently) prefer to approach the diagnosis of pulmonary embolism:
Note that “Scan for PE” really means to be “offer patient scan for PE”, considering relevant diagnostic uncertainty and risks in a shared decision-making process. “Other reason why d-Dimer would be elevated” takes into account clinical judgement regarding the uselessness of d-Dimer as an acute-phase reactant or inflammatory marker; many “sick” patients will have elevated d-Dimers, obviating its value as a one-way screen-out. Also, this chart does not account for any medicolegal liability risks – a wonderful perk of practicing in Texas.
Follow-up: Seth Trueger and John Greenwood pointed out on the original that there are some specific moderate- and high-risk cases that satisfy PERC criteria, and perhaps the risk-stratification step should occur before application of PERC, as is traditionally done. Fair enough! They also note the EMCrit flow-chart begins with an exhortation of “Did you really care about PE?” – which, I’d say, is approximated by my value judgement of “Bad miss?” after starting to consider PE. Finally, Scott Weingart chimed in to suggest, for patients in whom you’re playing the minimal-harm game for unexciting pulmonary emboli, a bedside ultrasound to quickly check for an occult DVT that might cause them to come back with clinically significant pulmonary venous thrombosis.