You finished the 'cast,
Now get CME credit

Not a subcriber yet? Why the heck not?
By subscribing, you can...

  • Get CME hours
  • Support the show
  • Write it off on your taxes or get reimbursed by your department

Sign Up Today!


Subscribe Now

If you enjoyed this post, you will almost certainly enjoy our others. Subscribe to our email list to keep informed on all of the ED Critical Care goodness.

This Post was by , MD, published 4 years ago. We never spam; we hate spammers! Spammers probably work for the Joint Commission.


  1. Mike says

    Ok Weingart, i’ll bite. Fueled by the fact that i am post shift, it is 3 am and the dogs woke me up and i have had a beer. This algorithm is completely nuts!
    Maybe i am an ignorant slut but……..
    PERC was studied and validated as a stand alone rule to obviate the need for testing AT ALL. Unless Jeff Kline has done a bunch of new, large studies incorporating PERC + dimer or PERC + Wells or PERC + wells+ dimer then all of these new algorithms are just more mental masturbation strewn with unproven assertions and leading us down the garden path.
    Even Kline, in a recent podcast somewhere advocated the use of PERC + dimer in pregnant women, but he had the decency to say it was based on nothing but his opinion (ah, the glory days oc critical thinking and the fallacy of reference to authority!).
    Think about it, PERC and Wells overlap so much that the addition of them doesnt gain you much other than a couple more criteria you have to meet to not do the workup.
    You cannot, nor should you attempt to rule out every PE. The vast majority of PEs do not represent a disease state, they represent a functional physiologic responsibility of the lung, to prevent small venous emboli from entering the arterial circulation where they can do real harm
    It is my belief that espousing these attempts to get to zero risk causes far more harm than good and people advocating this approach are effectively establishung a standard of care that is truly dangerous and irresponsible.
    Ok there you have the Jasumback opinion, worth precisely what you paid for it, and in the immortal words ofnone of the great thinkers of our time……”that’s just my opinion, i could be wrong”
    With greatest respect and appreciation for the forum to vent,
    Michael A. Jasumback, MD

    Ok whose idea was it to let me near a keyboard after drinking.

    • says


      You lost me there. PERC negative in the diagram = stop w/u; no d-dimer or imaging.

      PERC use already acknowledges that we are not trying to get to zero risk. The diagram is built-in acceptance of the 2% acceptable miss threshold.

      Tell me my friend where we have parted ways on our journey????

      • Paul rn says

        Hi Scott

        I’m an rn. Just wondering. Stable looking patient. Absolutely no distress. Reports some recent sob and generalized weakness (has a hard time getting things off the shelf at his job as a dishwasher. Dry cough. Hr 107. 35 male. 101.4. 1 episode of blood tinged sputum “a little bit”.

        Was worked up for pneumonia. Cxr normal. WBC nl.

        Resident was suspicious for pe. Now is like “ok ctpa for pe”.

        Is it ethical to send this patient for a ctpa without sending a d-dimer? I did not protest but it seems like the chances of this pt dying in front of me are extremely low vs the risk and expense of irradiating him for what ended up being a negative ct.

        Any thoughts? I feel like I should have spoken up.

        Looks like wells criteria makes him a 2.5.

        I’ve seen this recently, going straight to ct with no d-dimer on a patient who’s not too far from falling asleep. I’m not sure what difference 45 minutes would make to wait for the test.

        Would love your thoughts?


    • Martin says

      You are partly right Mike.
      PERC can be used in this setting but after the Well’s moderate arm. Well’s low is low enough, we do not need to double check this one, but if you get a moderate just double check with PERC- if it passes PERC do not bother with a D-dimer.
      Personaly I do the opposite- if someone fails PERC, I go on to do a Well’s to see if I can stop doing a D-dimer. This was very elegantly suggested by Dave Newman in his PE talk on

      • says


        PERC can absolutely not be used after Wells moderate, not sure where you got that. As to Wells low being low enough, that is merely conjecture at this stage. David’s assertion very well may turn out to be true (most of them are), but the evidence is contradictory and you certainly are unlikely to get below 2% unless you are including a bunch of pts who should not get a PE work-up in your cohort.

        Your assertion that a moderate Wells can be ruled out with PERC is dangerous and not even suggested by David.

  2. Haney Mallemat says

    If I understand it all correctly, PERC was intended to rule out someone who is low risk for PE by clinical gestalt. Adding Wells to the mix permits an objective way to call a patient low-risk. I completely agree with the point Dr. Jasumback that we should not try to find and treat every single PE, however I do not think that we need a randomized control trial to validate the algorithm above because it makes sense and was built into PERC as clinical gestalt (…aren’t prediction rules simply objective clinical gestalt anyway)?


    • says

      Haney, absolutely correct! In fact most people are not using the PERC as it was validated, b/c they are supposed to first ask themselves the question of whether they believe the chances of PE are <15% before they even think about using PERC. Unfortunately as Nickson and other listeners have pointed out, this is still not objective b/c the only thing we are using Wells for is to get the gestalt piece.


  3. matt says

    Sober and well-rested, and your diagram looks good. in short, PERC helps you find those patients whose pre-test prob of PE is below the d-dimer test threshold. also, of important note, it was validated on patients who stated “Shortness of breath” was the reason they came to the ED (or, of equal importance to cc), so applying it to every misc “chest pain” patient is a bit of an EBM stretch… Although seems to be done on a routine basis. interested in your thoughts…

  4. says

    Matt, do you mean Wells or PERC for SOB. Wells has been done on a ton of different ED populations, and in all the low risk is <6% (safe for PERC territory). PERC has also been looked at in a few, though less, ED populations; though as Dr. Newman points out nobody has yet done the study where you use PERC and send the patient home based on it and then follow these patients rather than just collecting PERC and seeing if they have a PE or not.


  5. Mike Jasumback says


    I think it was around the 2nd beer that things might have gone south, but perhaps not……

    More succinctly this time, then.

    My understanding of PERC is that PERC negative gets you to no testing. I’d have to go back an look at the derivation and confirmation studies. But basically I think it went something like, I think this pt COULD have a PE. If PERC- then no testing.
    But now we’ve added stuff. So now it takes WELLS low + PERC – to get to no testing. And I don’t know that that assertion has been tested.
    With respect to Wells moderate plus d-dimer , your algorithm tells me that a Post op pat, HR>100 and history of PE plus hemoptysis can be ruled out with a neagitve d-dimer and that doesn’t meet the smell test.
    Haney is right, decision rules are “objectified gestalt”, but I daresay that most of us would not rule out the above pt with a d-dimer (the dimer is going to be positive anyway since he is postop, but maybe not at 4 weeks?).

    I’m not sure that that helps any, but from our previous emails, THIS IS PRECISELY THE TYPE OF DISCUSSION THAT NEEDS TO BE HAPPENING on all sorts of fronts. With all the podcasts, and all the questions that are raised.

    Thanks again,


    • says

      PERC was validated by first asking the clinician what their gestalt is for PE. If you do Wells’ first, all this adds is it forces you to answer this gestalt question. Nothing else in Wells’ is different than PERC (even malignancy alone doesn’t take you away from low). No need for validation, this is just a way to get people to do what they are supposed to do any way.

      Not sure of the smell test, but high sens d-dimer is probably superior to most imaging we have available. The numbers are there in countless studies. ACEP’s clinical policy will support you in this practice as well. With the current crack-down on radiation, if your hospital doesn’t have a high-sens d-dimer then they probably should be getting one ASAP.

      The d-dimer is going to be positive anyway probably doesn’t ever hold water b/c sometimes in that 85 y/o it actually comes back negative, especially with the higher spec of the newer versions of the high-sens d-dimers.

      cheers my friend

      p.s. i like you with a few beers in you; you get all fiery.

  6. Mike Jasumback says

    One more thing…

    What this illustrates is the problem in all of clinical medicine, the a priori point estimate of probability of disease. This is not, and can never be, objective. Why, because you have to start somewhere.
    In your new algorithm, the first box illustrates that. What is that driver, that symptom complex, that gut instinct that gets you to “This patient might have a PE” ? It is from there that you have to generate a point estimate of disease probability, appropriately use a tool of some sort that has been verified in a population (but most likely not using your undefined clinical gestalt), to push your post test probability to an acceptable risk range.


    • says

      I don’t look at it as a problem, I look at it as the reason for our existence. If everything could be protocolized, what is the point of physicians?

  7. Burns says


    I like the thought process and algorithm, but Newman has made the point that PERC and Wells are mutually exclusive and can be used separately; if either is negative the workup can stop.

    However, I generally use them together as well, though I might move PERC above Wells in the algorithm. i.e.–PERC negative => stop the workup, PERC Positive => Apply Wells criteria as you have written. This makes a little more sense from a binary perspective. I don’t think you need the first question either, since that is already addressed in the clinical gestalt portion of PERC.

    I think Mike makes some great comments above–I get to reply only because I am equally impaired. I just woke up from the overnight shift, have had only one cup of coffee and am still fuming that there doesn’t seem to be a single hand surgeon in the country taking call on the one day where getting drunk and holding onto firecrackers or as long as possible becomes the national pastime– sorry digression)

    “It is my belief that espousing these attempts to get to zero risk causes far more harm than good and people advocating this approach are effectively establishung [sic] a standard of care that is truly dangerous and irresponsible.”
    –MA Jasumback


    I think Kline has been maligned heavily for his work on PERC, which is a shame because I love the fact that his work really allows us to use EBM to discuss an acceptable miss rate. The fact that we can support a decision with data that makes a patient “low risk” not the impossible “no risk”, and discuss the harms of excessive testing in a forum like this is the greatest contribution of Kline’s wok.

    Sorry about the flight of ideas and keyboard diarrhea (this is why I don’t have a blog).

    Keep up the great work,

    WWWD- What Would Weingart Do? Our EMCRIT community motto.

    • says

      Only reason for the first question is that some have started using PERC and d-dimer as SCREENS for PE, which actually increases imaging rate instead of decreasing it. This is one point that Dr. Newman and I agree on. If you don’t think the patient has a PE, don’t do PERC, Wells, or d-dimer…

  8. Burns says

    I agree that inappropriate use of D-Dimer (and medical decision make rules in general) is a travesty in medicine, but for the purposes of building an algorithm I’d put clinical gestalt in there only once. I think PERC uses a suspicion of <15% which is probably adequate for the first question.


    • says

      Don’t mean to belabor this, but nope. First question asks you is your pretest < 2% before starting a work-up--if so stop. PERC gestalt question asks you, "Ok, it is >2%, but is it < 15%?” Two very different questions.

  9. Burns says

    I think it gets hard to quantify gestalt, but I see your point and that does make more sense in the context of the algorithm. . .thanks for the forum.

  10. Mike Jasumback says

    Maybe I misunderstood PERC (and I haven’t gone back and looked at the validation study) but I thought it was stand alone for the low risk pt (<12-15% ), and that's where my hearburn lies. I have always found that the clinical gestalt and Wells rules aligned closely enought that I never applied Wells formally to get to that low risk number.
    I have also undestood that the low risk pt (<12-15%) with negative d-dimer got the post-test probability low enough to stop testing.

    As for the clinical assesment question, I agree, that is the reason for our existence as physicians. I've always said, people pay me for my judgement and not much else.

    And as for beers, if I make Essentials, I'm buying


    • says


      Absolutely true, you have no need of Well’s before PERC, you can just answer the gestalt question. When you put Wells next to PERC what you will find is the only thing putting it before PERC does is makes you answer the gestalt question. There is no other effect.

      Good d-dimer will take your low and

        intermediate patient

      to a post-test below test threshold.

      as to essentials, sounds good!

  11. Mike Jasumback says

    And by the way, don’t you people have lives? It’s the 4th of July for Gods sake. Go hold a firecracker or something. (just don’t do it in far northern California, I don’t have a hand surgeon either)
    At 3 am there were no comments on this now we are at what, 20? We need lives..

    oh well, sober, moderately well rested and off to the 4p-1a shift, yippeee


    • says

      I’m working; I don’t know of the others’ excuses, but remember most of our audience is not in the States and some probably rue the 4th as loss of domain.

  12. Mike Jasumback says


    Reference for the Intermediate Probability Pt? I’ve been using dimer for low prob pts. But not brave enough to get into those I’d call intermediate i.e. >12-15% pretest probability


  13. says

    Here are just a few from a quick search, there are quite a few more out there:

    Thromb Haemost 1998;79:32–7.

    Arch Intern Med 2001;161:447–53.

    Hematology. 2009 Oct;14(5):305-10.

    AJR Am J Roentgenol. 2009 Aug;193(2):425-30

    Systematic Reviews
    Thromb Haemost. 2009 May;101(5):886-92.

  14. matt says

    I meant PERC, but mea culpa, while the initial PERC validation was limited to those SOB pts, indeed the larger prospective MCT validation included almost half with cc of CP…
    Thnx, lead on,
    (less rested, less sober… Happy 4th!)

  15. Minh Le Cong says

    Hi Scott et al
    I love it when you Yanks get drunk and have a fight!

    I had questions about imaging and your proposed algorithim, please. What imaging do you refer to?

    And in the Wells criteria HIGH RISK in your algorithim you proceed straight to imaging. If that is reported as negative, what would you do next? Perform a sens D Dimer and back track? Or rely on your gestalt and ignore the imaging report?

    thanks and appreciate the debate here for my own learning

    • says

      Hi Minh and the rest of the EMCrit crowd,

      This what we do at Charlies once we’ve decided we need to do imaging (i.e. low/int PTP and positive D-dimer OR high PTP based on Wells with D-dimer not indicated):

      CTPA negative
      • Rules out PE if low or intermediate PTP on Wells score
      • If high PTP do CTV or leg USS – if negative then NO PE

      CTPA positive
      • PE regardless of low/ int/ high PTP

      Certain patients we don’t (usually) do CTPAs on:
      • Female <45y
      • Pregnant
      • CTPA contraindicated

      These patients have VQ SPECT (ideally with no underlying lung disease and a normal CXR for best results):
      • Negative – rules out PE even if high PTP
      • Positive – diagnoses PE except if low PTP – then get a leg USS, which if negative may need to be followed up with a PE.

      Also, we have a highly sensitive D-dimer assay that rules out PE if the Wells score is low or intermediate PTP.

      Exactly what you do depends on the performance specs and the various types of imaging modalities you have at your disposal at your institution.

      I agree with all of Scott’s responses above (what a suck up, eh).

      I view the need for a Well’s score of 0 or 1 as check on the the clinician’s gestalt when using the PERC score – not all of us are uber clinicians with supernatural gestalt senses!

      There has also been some discussion above of what the PTP needs to be for PERC to work – the docs in the Kline 2008 validation study said they thought the risk of PE was <15% before PERC was applied, but in reality the performance characteristics of PERC rule were such that it can be applied to a PTP of 10% – or if you are cautious, then ~7% (the lower limit of the 95% CI). I have tried to spell these calculations out in a post on LITFL: ‘Puzzling out the PERC rule’: which was written before the Hugli 2011 study using the revised Geneva Score. At some point I'll look at updating the post based on my opinion of that study.

  16. Casey says

    HI all
    I have a neologism for you, one I constantly employ – lets call it “schizogestalt”.
    Definition: Schizo`ges`talt
    This is when you have a patient referred by helpful nearby doctor who orders a blunder-bust of blood tests including a D-Dimer – which is weakly positive, then sends the patient in for a ?PE workup to ED. The patient looks great, healthy, and maybe has a few risk / Well’s points. However, it all hangs on the big 3 points for: “PE is most likely diagnosis”.

    So here is what you do – you split your brain in half and try and work out your ‘gestalt’ whilst ignoring the knowledge that the D-Dimer isn’t quite normal. This requires a healthy degree of self-delusion. Cos’ I reckon once we see the + D-dimer we get all iffy about not imaging, no matter how low the Well’s score is.

    So work on your schizo-gestalt, you might irradiate less folks!

  17. Andy Webster says

    The minefield that is VTE… many different pathways so many different views. Should keep researchers in a job for many a year to come. At the same time will mortality and morbidity from VTE actually reduce, or we we just find more small PE that would never cause harm?

    • says

      “At the same time will mortality and morbidity from VTE actually reduce, or we we just find more small PE that would never cause harm?”

      This was in the discussion but the Weiner paper in May 2011 in Archives of Internal Medicine answers that pretty definitely as the latter:

      Wiener RS, Schwartz LM, Woloshin S. Time trends in pulmonary embolism in the United States: evidence of overdiagnosis. Arch Intern Med. 2011 May 9;171(9):831-7.

  18. says

    Great stuff guys

    enjoyed watching the video till the 60 min mark and my cellphone bandwidth allowance ran out! I’m on holidays and away from the joys of broadband!

    My two cents (or maybe more than that…)

    I think Scott’s added question (do you REALLY think it’s a PE) in the image is key – the thing with all the PE studies is that someone has to suspect a PE as a possibility to even get into the study and have the 50 point data sheet used. So the factors that go into why a doc enrolls them in the study are really important.

    As Master Nickson says, the gestalt is the most important part of the rule. I would argue that the gestalt comes even earlier before the rule is even derived.

    I have seen multiple cases of truly asymptomatic PE (my own Dad being one!) – incidentally noted in ICU patients and cancer patients picked up on scans for other reasons – these type of patients aren’t even covered in these studies as no one suspected it.

    Which is why I think we’ll always be a bit buggered when it comes to PEs. Wells and PERC are useful no doubt, but only as far as they go. That helps keep us docs in a job and stop us getting replaced by an iPhone that’s able to put IVs in.

    It seemed that some of the debate in the video was whether the low-risk group in wells were <2% or around 3% or so. Did i pick this up wrong? If so then the issue doesn't seem to be whether it's 2 or 3% but rather if 2% is an acceptable miss rate. i think probably higher than 2% is acceptable but i think that question is unanswerable till we work out if all these bloody PEs matter or not

    (here i stand on my soapbox and wave good bye to the evidence…)

    PE is a widely varying beast. We've surely all seen sick PEs and well PEs. No doubt some of the well PE patients can become sick ones but we don't really know if that happens rarely or commonly.

    My guess is that some of the small PEs (esp in low-risk populations) receive precisely zero benefit from anti-coagulation.

    And i know no one's gonna do a placebo trial on this but using some of the data already out there is there anyway we could look at the wells low-risk groups (2% or 3% or whatever) and see how they did at follow up compared with the high risk groups. I don't see this in most of the papers; a diagnosis of PE being the only outcome normally measured.

    i know there's stuff out there to stratify the bigger PEs (echo, trops etc…) but we can diagnose them easily, I want to know if i can stratify some of the smaller PEs to NO TREATMENT.

    If we knew that wells low risk groups (or some other set of criteria) predicted good outcomes no matter what then we wouldn't have to worry about all this.

    I know that last rant is deviating from the discussion a bit.

    And to follow up on Casey's point about having to fly 1000 miles to get a scan – we do V/Q scans mainly (CTPA for the obvious sick ones) and we can only do these on wed or fri mornings and only when the isotope is in stock. And after a session on our knees begging the radiologist. Hardly a 1000 miles but still gives you pause to think!

  19. says

    First, thank you all for the incredible comments!

    To answer some of the questions posed in the thread:
    We use CTPA for pretty much everyone, unless their renal function is crap. My personal belief (and I think Jeff Kline’s as well) is that even in high risk, a well done CTPA negative = done. PIOPED II unfortunately got it totally wrong. I believe an angiogram is no better than CTPA at this point, and a negative CTPA probably predicts pts with a good prognosis without treatment.

    I think it is clever to get d-dimer in the high risk pts as well, b/c a neg CT and a neg d-dimer and you are definitely done. If they are high risk, it is also cheap and easy to get a bedside sono of the deep veins. High risk get f/u for formal dvt study as an out-pt.

    David and I discuss points very similar to the ones you discuss in the last 30 minutes–great minds think alike.

  20. Minh Le Cong says

    thanks Scott et al

    I am not convinced by your advice to perform a D Dimer in the high risk patient with a negative CTPA. It would seem more logical to do the cheaper , radiation free test first in the high risk group. What would you do if you had a +ve D Dimer and -ve CTPA in a high risk patient?

    Could you not assess for Wells criteria and if high risk then do the D Dimer. If positive you treat? If negative then you are done? With safer anticoagulation options already for things such as AF and likely DVT/PE in the near future I imagine empiric therapy is more practical and reduces diagnostic workup

    • says

      D-dimer is a non-specific test: positives mean virtually nothing. Certainly not enough to move even a high risk patient above the “treatment” threshold. High risk patient with Neg CTPA and + d-dimer needs a dvt study, whether it is bedside or formal ultrasound or CT leg veins based on the current evidence.

      Giving a false + dx of PE has ramifications far in excess of the initial anti-coag. Every time this patient comes to an ED with chest pain, sob, or tachycardia they are going to wind up with a PE w/u. They will have problems getting life insurance and health insurance will be more expensive. And anti-coagulating a 75 y/o is a lot different than a 35 y/o being that the latter may still want to engage in sports, skiing, etc.

  21. Minh Le Cong says

    Scott, I admire your energy for teaching and debate when you are up posting at midnight!
    I don;t think the issue is as black and white as it may initially appear. Andy is right that this is a grey area of clinical practice. Take the use of gestalt in the decision making. This is so non standardised that its use is hard to define. In essence we are saying gestalt=clinical experience and that as we know is not something uniform nor standard. It is as you say the reason why we still need human brains in point of care medicine. I am aware of gestalt getting docs into a lot of trouble when treating hypotensive, tachypnoeic pregnant women for suspected PE and pushing heparin when it has been a ruptured ectopic or AFE from uterine rupture.

    AS for the CTPA and imaging I find this even more grey as it depends upon the interpretation and provider. I have had two radiologists report the same CTPA differently and in the end you got to make a clinical call in regard to advising the patient on diagnosis and therapy. In pregnant women we see this all the time where CTPA is not done usually and VQ scanning is the norm. How Many intermediate prob scans do we get..a lot and so in that case you gotta make a call. Its not uncommon the call is to err on the side of caution and treat empirically for the rest of the pregnancy with LMWH.

    AS for D Dimer I think you contradict yourself when you say a positive result is meaningless then go on to say if it is positive in the high risk patient and -ve CTPA then they need a DVT workup. So it is not meaningless if it causes you to think and look more.

    But its good to hear the different sides of the debate and at least you put yourself out there by proposing a better decision making process.

  22. says

    Minh-of course we will always need to be clinicians in the gray zones.

    I’m not sure how I am contradicting myself. The nature of a sensitive, non-specific test is that a negative can have dramatic effects on your w/u, while a positive doesn’t affect your probability and you continue the w/u as if the test did not exist. If there was no such thing as d-dimer, you would need to proceed to further testing after a negative ct in a high risk patient (at least in the vision of the US organizations), so you do the same in the case of a positive d-dimer.

    • Minh Le Cong says

      thanks Scott

      What if you were in a remote area, like Antarctica? You got someone with High risk Wells presentation and positive D Dimer? Do you wait for the CTPA before starting anticoagulation?

      Sure you can get a portable USS for DVT but if that is negative do you still wait for the CTPA in the tachycardic, tachypnoeic, pregnant patient? Even though it will take 3 days to retrieve them to a CTPA machine? And by that time the PE signs may have resolved on imaging?

  23. says

    2 things – why would you even bother with a d-dimer in this high risk patient in Antarctica? And secondly, in general the selection of people to head South tends to avoid sending pregnant women…as for what happens when folks get there, well, I have heard some stories…

  24. Minh Le Cong says

    OKay good point, my use of pregnant patient was not the best example. My point really is what would you do if you had to wait a few days, weeks to get your CTPA in that high risk patient. Is it so vital to your diagnostic workup that you simply cannot do anything until you get that CTPA?

  25. says

    Just watched the last 30 mins of the video, i now see how my comments are kind of redundant!

    If you’re so afraid of getting sued in the US over non-diagnosis/treatment of PE then you can do the trial here in Ireland as we’re almost a 3rd world country these days and can’t afford all the CT scans so we’d love a reason not to do them!

  26. Mattia Quarta says

    Sounds great and reasonable.
    Although the starting questionI think is really the key point.
    Nonetheless if you really (really!) start thinking about PE in a let’s say young patient healthy looking shound’t you answer yes to the tricky question: PE is the first diagnosis or equally likely?
    I guess everyone has felt uncomfortable with this criteria of the Wells’ score in the very beginning of his residency, since the question is cloudy enough to be a test of self confidence. With time I’ve started thinking it was subtly included to solicit cliniacians to wonder whether it is really worth to go on with the work up rather than increasing the risk of the patient yo’ve been evaluating.
    Therefore I’m asking wound’t it be more useful to use the Geneva score? It won’t have any overlap with the PERC rule and it’s more objectuve. Proabably the math do not allow this.

    • says


      That is exactly what I used to advocate. Low risk geneva should take you below 15%, which seems perfect for the PERC rule application–it was beautiful! Until Hugli’s article (pubmed link) showed that low risk geneva negative PERC still has a post-test prob that is too high.

  27. Mattia Quarta says

    Definitely have missed that pubblication and maybe quite a lot relevant others. I’ll go through it eagerly, and eventually leave the kids with any excuse to grandma more frequently.

    I’ve read all the comments now and I apologize since my post was largely inapt beeing the answer

  28. Mattia Quarta says

    already adressed by Nickson.

    One more thought if you allow me: do we all have the perception that a certain amount of episodes of small PE occurs probably with no or subtle symptoms all life long. As if it might be a sort of physiological process as much as atherosclerosis is for the non pulmonary circle? After all centuries of natural bleeding selection should have favoured thrombophilic profiles.

  29. Mattia Quarta says

    A small amount of small PE that cause some pleuritic discomfort whether or not accompanied by mild dispnea could be tolerated as just overnatural events without any anticoagulation therapy?

    Scott Keep going with the PE brain-storming it’s just great!


  30. says

    In response to Mattia’s penultimate comment above, the AHA’s March 2011 paper speaks to the concept of CTEPH (Chronic Thromboembolic Pulmonary Hypertension) which appears to be fairly nebulously attributed to “one or more” previous PEs, despite stating that “up to 63% of patients with CTEPH were not previously aware of having had a PE.” I have a few doubts about the breadth of this link to begin with, and one wonders if there is a bit of a backlash in the “establishment” to the idea that perhaps we shouldn’t be panicking so much about finding every last tiny little subclinical (and even physiological) PE. I am prepared to accept that a couple of big PEs is going to end up giving you pulmonary HTN, but I struggle with the “63% not knowing they had a PE” that is quoted in the paper, which would suggest that CTEPH could come from subclinical PEs – There doesn’t appear to be any real evidence for this on my reading, but I must admit I did lose interest in what is a fairly tedious and involved document.
    (Management of Massive and Submassive Pulmonary
    Embolism, Iliofemoral Deep Vein Thrombosis, and Chronic
    Thromboembolic Pulmonary Hypertension – Circulation published online Mar 21, 2011;)

  31. Steve says

    Pretty late to this discussion but I’ll throw in my 0.02…I think this diagram is the way that we all have been practicing for a while…however I love the first step…”Do you think it’s a PE” and if the answer is no, stop there. That way we don’t even mess with Well’s or PERC or anything else- we just say NO and move on.

    I haven’t been explicitly using Well’s to risk stratify people before using PERC but in reality I have been doing that on a subconscious level. I agree with the use of the d-dimer- if you have someone who is otherwise low risk but PERC positive (usually its tachycardia or on OCPs) then that is where a d-dimer comes in. Otherwise, don’t order that $%$#! test.

    Don’t get me wrong, I love PERC…if we could find other variables to replace OCPs and tachycardia then we could avoid testing on even more people.

  32. andyb says

    How can you use two rules in a row? Its similar to using likelihood ratio in series, and that has never been validated, yet it makes sense.

  33. andyb says

    If you use the wells criteria to lower your pretest prob to less then 15% then using the perc to then again lower your pretest prob im not sure thats kosher? i mean the wells is essentially plugging a prior pretest prob and using the wells to generate a post test prob which then becomes your next pretest prob right? Is this like using the wells as a negative likelihood ratio and then again using the PERC as another -LR and i did not think LR tests used in series had ever been validated… however it makes theoretical sense.

  34. andyb says

    Scott, im not sure if i am making myself clear, you are using the wells criteria as a predictive rule to generate a negative predictive value , and i understand you can choose which rule you want to use. You could use either the perc or the wells and which ever one got you a lower value …yes you could use that! however i am not sure you can use one to generate a post test prob and then call it a pretest prob for another test ( the PERC )…?

  35. Mattia Quarta says

    I totally agree on this one. I was about to post a similar comment. I guess what Martin ment to say is that in Kline’s 2008 validation study even just PERC negative patients independently from clinical judgment had very good outcomes (only about 1% had VTE/death at 45 days). I guess this is what David Newman might have mentioned in his podcast. I think though this is not surprising since the profile of a PERC negative patient almost matches the one of a Wells low score one. Almost inevitably low risk patient HAD NO CLOTS!

  36. Duncan says

    I know this is an old thread but…

    I use the algorithm at the top of the page and it makes sense to me. I also know that we still overinvestigate. But I had a clinical scenario that still made me a little uneasy (there’s Gestalt creeping in again…) when I chose NOT to investigate.

    Well’s score 1.5 or 4.5 depending on the subjective question (I would go for 4.5), high sensitivity D-dimer negative. Stop investigating. Easy.

    However, this was a young patient, on the OCP, with a long haul flight (UK to Australia) four weeks before, with a story that could have easily been PE or not PE but with a persistent tachycardia up to 140-150 with normal axis and ST-T. There was no other convincing explanation for her tachycardia.

    My decision to stop investigating her for PE was made easier by the fact that she was admitted for her persistent tachycardia and I’d already given her LMWH (locally here, she’d get admitted for V/Q even if we kept pursuing it, so it would have no effect on her ED treatment), but I was wondering what others thought about the worrying tachycardia with Gestalt that favoured PE over cardiac causes. Are there symptoms or signs that are so convincing that we need a little more caution before we stop the workup of the low or moderate risk patient?


  1. “Time trends in pulmonary embolism in the United States: evidence of overdiagnosis..” Archives of internal medicine 171 (9) (May 9): 831–837 | Emergency Medicine Ireland says:

    […] Found this via a chap who commented on Weingart’s now famous PE episode. […]

  2. […] followed by the PERC rule to decrease the risk to less than 2%.  The algorithm below from best illustrates such an […]

Speak Your Mind (Along with your name, job, and affiliation)