Dear Thomas, I think we need clinicians to be more precise in these declarations. If we begin to train clinicians that Probable should mean ~85% probability +/- 5% then we will move closer to stability.
Although the goal of reducing uncertainty is in general laudible there are some problems that crop up first clinicians are usually only about 90% sure by evidence when they "make a diagnosis" if looked at from an EBM perspective. Also the path to reduction of uncertainty takes into account what prior data is available, the risk benefit ratio of obtaining each piece of data, and patient preference. Interesting but not easy. Peter Peter L. Elkin, MD Professor of Medicine Mayo Clinic College of Medicine > -----Original Message----- > From: owner-openehr-technical at openehr.org [SMTP:owner-openehr-technical at > openehr.org] On Behalf Of Thomas Beale > Sent: Wednesday, April 20, 2005 6:59 AM > To: openehr-technical at openehr.org > Subject: Re: Dr R LONJON Confidence indicator ! > > Elkin, Peter L., M.D. wrote: > > >Dear Roger and Thomas, > > > >We have looked extensively at Multivalued logic for quantitating > >uncertainty. It turns out that most folks in that world have taking 0 false > >and one true with a number of discrete, usually equally spaced values in > >between for uncertainty. > > > >After a longwinded go around with a Prof of Philosophical Logic at Princeton > >(Dr. Graham) We determined that there at least three reproducible types of > >uncertainty (with good inter-rater reliability) and ~ seven semantic > >categories. > > > >The types are Probable (our guess is around 85% true +/- 5%) and Unlikely > >(our guess is around 15% true +/- 5%) or Just as likely as not (again our > >guess is around 50% +/- 15%). These number come from the average PPV of the > >evidence when a physician "Makes a diagnosis" and NPV when a physician rules > >one out. > > > > > [with appropriate excuses in advance for my engineer's view of clinical > things;-] > > I presume that these values (which seem entirely reasonable to me) were > obtained by a statistical study of clinicians' notes? Or interviews? But > the problem we are always concerned with is: what does one clinician > mean when s/he says "probable rheumatoid arthritis"? We can't assume it > can be translted into 85% +/- 5% can we? The particular physician who > said it might habitually and unconsciously put "probable" all over the > place, when they should really put "possible". Sam's point of view so > far has been: make them enter a number (prompt = "% probability of being > true" or similar). I know that doesn't address the perfectly reasonable > need to allow clinical people to write "probable", "possible" etc, so > maybe it's not a long term answer. > > But let's just consider what doing clinical medicine is about: it's just > scientific problem-solving. The goal is to fix a problem (with the > patient); the method is to iteratively gather information until a > conclusion (diag = Rh Arthritis) can be drawn or a decision can be made > (commence ibuprofen). Fixing a problem may involve many repetitions of > this until the problem is fixed. Now, whenever (lack of ) confidence or > uncertainty occurs, it means that we don't have enough information to > make a decision or draw a conclusion, at least not the next one in the > chain. But we do have an indication of what to do next - usually gather > more information. > > So perhaps the way we view words like "possible", "likely", "probable" > should be as motivators to perform more actions to reduce the > uncertainty. If a doctor writes "possible malaria" re: a patient just > back from a holiday vietnam, with heavy flu-like symptoms, the obvious > implication is to do the appropriate microscopy & other diagnostic > procedures for malaria, to rule it out or otherwise. For most diseases, > a diagnostic algorithm or guideline is available, and the physician > > having used a word implying uncertainty just means that the diagnostic > process is currently at some interior node of such a guideline tree. The > key question is probably _which_ of the possible next steps to rule out > /rule in one of the differential diagnoses to do in which order - i.e. > which is cheapest, fastest, most relevant to patient health etc. > > So my question to clinicians is this: doesn't a note containing > "possible X", "likely Y" really imply a differential diagnosis, even if > only one of the possibilities is actually noted? If so, it may not > matter what the level of uncertainty is so much; what matters (among > other things) is the severity of the consequences of any of the possible > branches of the differential diagnosis. E.g. if one of the implied or > noted branches of a differential diagnosis for a patient presenting > fever is malaria, presumably both patient and doctor want to discount it > as fast as possible, and pursue the appropriate steps to do so. But if > none of the branches is life-threatening, reasonable action may be "wait > 12 hours" and re-assess. The very common situation of infant presenting > with fever must present such a quandary daily. > > I'm wondering if there is a meta-algorithm of some sort lurking behind > the scenes, which takes account of uncertainty in a note, and also > severity of non-discounted possibilities, as a way of deciding what to > do next. There is undoubtedly published work on this... > > thoughts? > > - thomas beale > > - > If you have any questions about using this list, > please send a message to d.lloyd at openehr.org - If you have any questions about using this list, please send a message to d.lloyd at openehr.org
