Cutting Through 36 Calculators: How to Actually Diagnose a PE

Type "pulmonary embolism" into MDCalc's search bar and you get 36 results. Most clinicians don't have time to sort through all of them when a patient is sitting in front of them, and most don't need to. MDCalc’s new feature, Collections, now helps clinicians navigate these scores more effectively. 

Host Dr. Joe Habboushe, co-founder and CEO of MDCalc, sits down with Dr. Eric Steinberg to walk through the diagnostic side of pulmonary embolism, the tools featured in the new multi-society PE guidelines, and why so many of them get misapplied at the bedside.

Meet the Guest

Dr. Eric Steinberg is an emergency physician and residency director. He and Dr. Habboushe have been talking through PE cases together for close to 20 years, going back to when Dr. Steinberg was a resident under Dr. Habboushe's supervision. Dr. Steinberg recently presented on the new multi-society PE guidelines, which is what prompted this conversation.

The Real Risk of a CT Scan

Often, clinicians default to scanning any patient where PE crosses their mind, reasoning that a scan is the safe choice. Dr. Steinberg argues the opposite is often true. Radiation and contrast are the risks people think about, but the largest source of harm turns out to be incidental findings and false positives that lead to unnecessary treatment, including months of anticoagulation a patient never needed. Jeff Kline, creator of the PERC rule, built his 2% pretest-probability threshold by adding up all three categories of risk and found that the incidental-findings bucket dwarfed the other two combined.

Why PERC Only Speaks in One Direction

One of the most common mistakes Dr. Steinberg sees in training is treating the PERC rule as bidirectional. PERC can tell you that a patient is low-risk enough to skip a workup entirely. It cannot tell you the opposite. A patient who fails PERC, even by one criterion like age, hasn't been shown to be at higher risk. They've simply fallen outside the rule, and clinical judgment takes over from there. Dr. Habboushe makes the same point about other one-way rules in emergency medicine, including the Canadian CT head rule, where failing to meet criteria doesn't mean a scan is required.

Wells, Geneva, and YEARS: Choosing the Right Pretest Probability Tool

Once a patient falls outside the very-low-risk range, the conversation turns to pretest probability. Dr. Steinberg breaks down when he reaches for Wells versus Geneva: Wells incorporates clinical gestalt, including whether PE is the leading diagnosis on the differential, which makes it more useful for clinicians who've built up years of pattern recognition. Geneva is fully objective, which he recommends for residents and clinicians still developing that judgment. From there, the YEARS algorithm gets its own segment, since Dr. Steinberg pushes back on the common misconception that it's a pregnancy-only tool. Its real value is a flexible D-dimer threshold that adjusts based on patient risk factors, useful well beyond obstetric cases.

What's Next

This episode covers the diagnostic side of PE: the four core tools most clinicians will use on the majority of patients, plus a look at age-adjusted D-dimer and altitude-adjusted PERC for edge cases. Part 2 picks up where this one leaves off, once a patient has already been diagnosed, and covers how to decide who can safely go home, who needs admission, and who needs a higher level of care.

MDAware: Upgrading Clinical Judgment is MDCalc's podcast dedicated to breaking down the science behind clinical scores and bringing transparency and confidence to your clinical workflow.