Layered Psychiatry

 

I had this idea about how to present the complexity of the psychiatric diagnostic and treatment process.  After putting up a couple of diagrams for comment, I went ahead with a PowerPoint. For about 15 years I taught a course in how not to mistake a medical diagnosis for a psychiatric diagnosis.  My audience at the time was 3rd and 4th year medical students.  The lecture included a discussion of the research at the time in pattern matching and pattern completion, heuristics and common biases, Bayesian considerations, and inductive reasoning. It was generally well received but really cannot be appreciated until you are a senior clinician.  Over the time since I taught that course there also seems to be a distinct bias toward considering DSM criteria to be the basis for psychiatric diagnosis and decision making – and that is clearly a mistake.

The very first time I really became aware of the importance of pattern matching occurred when I was a fourth-year medical student.  I was on an Infectious Disease rotation and my job was to get the consults for the day, go out and see the patients we would be rounding on, do my basic compulsive medical student work up and present the findings and my ideas about the case to the attending physicians. ID docs are very bright people and like most impressive rotations I contemplated becoming an ID specialist for a while.  My patient that day had spontaneous bacterial peritonitis and the question for us was: “Do you agree with the diagnosis and current antibiotic treatment?”  I met with the patient, took a complete history, did a physical exam, reviewed the hospital course and labs, and had time for a little research. At the time I was carrying a copy of Phantom Notes for Medicine – basically an outline of the major medicine text of the day. I looked up the differential diagnosis.  I was also carrying a copy of Sanford’s guide to antibacterial therapy – the 1982 version and looked up the recommended antibiotics for peritonitis.  I was all set for rounds at that point.

Both of our ID attendings were very serious physicians. There was not a lot of banter or joking.  I anticipated presenting all of the dry facts and either getting a brief agreement, some questioning until I could no longer answer, or a long discussion of the diagnosis and treatment.  In this case the attending came into the patient’s room. He was 15 feet away from the patient and he said: “What am I seeing from right here that is a potential problem?”  Our team consisting of the ID fellow, two Internal Medicine residents, and myself – stopped in our tracks.  Nobody had an answer.  Weren’t we here for peritonitis?  How can you diagnose that from across the room?

“What is wrong with the patient’s shin?” Dr. R stated looking as serious as usual.  Sure enough there was a light pink confluent rash covering about 10 square inches of the patient’s left shin area. Dr. R happened to be an expert in streptococcal infections. He rattled off the type of strep he expected and suggested that we get a culture and send it to his lab for confirmation. I completed my presentation.  The primary diagnosis and treatment by the medicine team did not change, but now there was a new diagnosis and treatment that depended on Dr. R’s ability to recognize the pattern of this rash and make a rapid diagnosis – even though he was not expecting it.  But beyond that – we all saw the rash (although we had to be prompted to see it). Dr. R not only saw it, he processed it as a unique rash, and then a rash most likely caused by a specific kind of streptococcal bacteria. And over the next several days he was proven correct by the culture result.

Pattern matching and pattern completion are critical skills acquired by clinicians over the course of their training and careers that allows for not only more rapid diagnosis and treatment but also more accuracy in classifying ambiguous cases. Some of the examples I used in my course included ophthalmologists compared with primary care physicians diagnosing diabetic retinopathy and dermatologists compared with primary care physicians across a series of rashes.  In both cases the specialists had a higher degree of accuracy and were better at diagnosing ambiguous cases.

Cognitive neuroscience encompasses a broad range of perceptual studies starting with the early studies of visual processing by Hubel and Wiesel to more recent studies that look at the encoding that occurs in perceptual systems and what level of processing occurs at the level of primary sensory and association cortices, what the higher-level cortical structures may be, and whether or not top down processing influences perception. According to Superior Pattern Processing (SPP) theory (3), both perceived and mentally constructed patterns are processed by encoding and integration and at that point can be used for decision making or transferring approximations to other individuals.  In my example, Dr. R not only sees the pattern of the rash, but it is integrated into a feature set that has a time, visuospatial, social, and emotional context that makes it more likely that he will make a correct diagnosis. Experimental data suggests that he is not seeing the rash like any other person in the room – largely as a function of top-down control of his perceptual process.  The actual transfer of this pattern to his junior colleagues is limited because they see the rash as being a universal truth – that is they just “missed it” and therefore need to memorize what this rash looks like and not let it happen again.  They are also unaware of the processes involved in pattern matching or processing or they might have asked him about it.  For example, a logical question would have been: “What features of this rash do you notice that are suggestive of strep or a specific kind of strep?”

The question of what represents a pattern is critical to the idea of pattern recognition and processing.  There is a natural tendency to associate the term with visual or auditory stimuli, but without too much imagining patterns can clearly exist in any sensory modality and often involves the integration of multiple sensory inputs.  Cortical organization generally reflects primary sensory input to the cortex with adjacent sensory association areas and further information flow to heteromodal areas in the frontal and temporal cortex where additional integration occurs. Patterns can be sensed, encoded, recognized encoded and processed across theses systems.  The resulting integration yields a very complex array of patterns that are not intuitive.  For example, Mattson suggests that pattern processing in the human brain forms the basis of human intellect including problem solving, language and abstract thought and that it includes fabricated patterns.  Those fabricated patterns allow vicarious problems solving without having to conduct real world experiments.  The recent cognitive neuroscience of pattern processing is a significant advance compared with the old diagnostic paradigms I taught 20 years ago.  Those old experiments were basically a comparison of a non-expert to an expert diagnostician focused on a relatively basic clinical problem like a pathology slide, x-ray, ECG, or physical finding and the results were not a surprise – the experts typically prevailed in both accuracy and speed.  The sheer amount of information in a clinical encounter looks at what is essentially an infinite array of patterns, including patterns that are generally not even mentioned as being clinically relevant.

In considering what kind of patterns that need to be recognized and processed by a psychiatrist – the patterns that exist in clinical practice are a starting point.  These patterns and the associated phenomenology have been grossly oversimplified by an overemphasis on nosology. I talk with far too many people who see psychiatric diagnoses as phrases on a page in the DSM. I cringe when I hear: “The patient does or does not meet criteria for (DSM diagnosis x)”.  Kendler was correct when he referred to the DSM approach as an indexing system.  It gets people into the same ballpark, but it is not be very useful for predicting response to treatment or that specific person’s response to being ill.  It is also based on a fraction of the information collected in a psychiatric evaluation. When I consider the feature sets that psychiatrists are considering in evaluations it may look something the graphic below.  Of course, these features sets are simplified for the purpose of making a useful graphic. They will vary with the individual, their experience, social context, and culture. They will also be blended across space and have their own individual levels of integration and patterning.  Let me provide a couple of examples to illustrate these points.

Consider the above diagram as representing the possible features that must be recognized in order to assess a patient presenting to a psychiatrist and formulating and optimal diagnostic and treatment plan. My overriding concern in the first few minutes of the evaluation is whether this person really has a psychiatric disorder or a misdiagnosed medical problem and as a corollary - are they medically stable? That sounds like a basic consideration but prioritizing it is not listed anywhere in the DSM or any medical text that I know about. It does involve rapid recognition of patterns of acute medical illness particularly the most likely patterns to be misdiagnosed as psychiatric disorders and what I am seeing in real time.  It also involves pattern recognition of the thousands of psychiatric presentations that I have see that were really medical disorders.  Real life examples have included an almost immediate recognition that the patient had a stroke (many cases), seizures (many cases), meningitis, encephalitis, cerebral edema, serotonin syndrome, and neuroleptic malignant syndrome.  These rapid diagnoses were all predicated on experience-based pattern recognition rather than written criteria and these diagnoses had nothing to do with the DSM at the time.

A more cross-cutting feature in the diagram would be transference issues and defenses that can arise as soon as the initial evaluation or be indirectly evident by the patients historical description of their relationships with important people in their life.  These patterns will involve several layers in the above diagram and most importantly may suggest a psychotherapeutic intervention that can be implemented as early as the original assessment.  A similar process occurs if the patient is describing features of a major medication responsive illness.  In that situation, features from multiple layers result in a pattern that may be recognizable to the psychiatrist in terms of specific medical treatments or the urgency of those treatments.

And finally - what might the graphical representations of these pattern matching processes be?  Here are a few examples.  In the case of psychotherapeutic examples, it will depend on the exposure to specific therapies in training and practice. Each therapy has a specific pattern or series of patterns that the therapy depends up as well as patterns more specific to the conduct of therapy.  These graphics contain critical books from my library shelves with those elements.  In the case of the diagnostic and treatment process - the school of therapy and potential application are important patterns to recognize in the initial assessment.

All of these books contain symbolic representations of clinical patterns in the form of vignettes designed to assist the student of psychotherapy in learning techniques. They also contain information about the patterns of intervention that are relevant for a specific therapy and in some cases the common factors required in all successful therapies. I have graphically represented what happens in pattern processing once a theme is noted in the clinical assessment of the patient.  Clinical teaching of this process is often problem identification followed by an algorithm of features that might predict a successful course of therapy or limitations in therapy based on the students knowledge level at the time. As is true for most pattern matching and processing, the more extensive a physician's previous pattern exposure - the more likely they are to match the optimal intervention to the problem. 

I will resist making this first post of the New Year too long and wrap it up at this point with a diagram that I think pulls it all together (see below).  Each layer of this diagram consists of patterns and all of the associated pattern processing that leads to psychiatric diagnosis, formulation and treatment.  A few of the key features include the fact that diagnosis and treatment are interchangeable processes.  There will be times even during the initial information gathering that a verbal treatment intervention needs to occur and the entire interview occurs in the context of empathy and what Ghaemi, et al (4) have described as an existential psychotherapy based encounter – even if the administrative focus is on pharmacology. A second feature is that the information exchange is necessarily large if the psychiatrist and the patient are capable of it. There has been no research that I am aware of on the optimal amount of information that is required, but there are many limitations.  The advent of the electronic health record for example has led to the universal use of templates that are very restrictive in terms of information, typically dichotomous responses. A third implicit feature is the concept of patterns, what they imply for diagnosis and decision making and how there is almost a complete lack of discussion about this process in an era where diagnoses seem to have collapsed to a brief list of bullet points.  Cognitive neuroscience is a critical area of research focused these processes that I first became aware of when reading Kandel’s book “The Age of Insight” (5).  It is an area that does not typically get a lot of attention from psychiatrists, but it is a logical extension of the work done by behavioral neurologists from 20 years ago.  If we really want to focus on how psychiatrists think about diagnosis and treatment – we need to study this field, especially as the experiments get more complex.

I will wrap up this post at this point with the hope that 2021 is a much better year and that mankind is able to put this pandemic virus behind us by the summer and approach future pandemics with more science and wisdom.

 

Happy New Year!

George Dawson, MD, DFAPA

 

References:

1:  Constantine-Paton M. Pioneers of cortical plasticity: six classic papers by Wiesel and Hubel. J Neurophysiol. 2008 Jun;99(6):2741-4. doi: 10.1152/jn.00061.2008. Epub 2008 Jan 23. PMID: 18216235.

2: Poirier CC, De Volder AG, Tranduy D, Scheiber C. Neural changes in the ventral and dorsal visual streams during pattern recognition learning. Neurobiol Learn Mem. 2006 Jan;85(1):36-43. doi: 10.1016/j.nlm.2005.08.006. Epub 2005 Sep 22. PMID: 16183306.

3:  Mattson MP. Superior pattern processing is the essence of the evolved human brain. Front Neurosci. 2014 Aug 22;8:265. doi: 10.3389/fnins.2014.00265. PMID: 25202234; PMCID: PMC4141622.

4:  Ghaemi SN, Glick ID, Ellison JM. A Commentary on Existential Psychopharmacologic Clinical Practice: Advocating a Humanistic Approach to the "Med Check". J Clin Psychiatry. 2018 Apr 24;79(4):18ac12177. doi: 10.4088/JCP.18ac12177. PMID: 29701934.

5:  Kandel ER.  The Age of Insight. Random House, New York, 2012.

Graphics:

All generated by me for a PowerPoint presentation by the same name.  The photo at the top are two pamphlets that I carried as a med student along with a copy of Phantom Notes.  I was carrying them when I was in the room with Dr. R as he made the diagnosis described above.  I would not trade my medical school experience for anything. 

They Don't Even Know What They Are Seeing.......

I was walking back from a meeting with a psychiatric colleague the other day.  There was the usual grousing about the practice environment and miscommunication and she made the following observation about why physicians and psychiatrists don't get the information they need.  She pointed out that in many cases the nonphysician  observers: "Don't even know what they are seeing."  If you are counting on people for observational data and that is true - that is a setup up for suboptimal care at the minimum and a catastrophe at the worst.

Take the case of a very basic measurement - blood pressure and pulse.  Anyone taking those measurements should be aware of the guidelines and whether or not the patient has a baseline abnormality, condition that can affect either, or medication effect that leads to changes in the vital signs.  They should also be aware of the limitations of measurement.  All of the automatic blood pressure machines in the world will not be able to assess and treat the patient unless the operators know what the numbers mean.  They also need to know that one of the problems with single operator and strictly machine operated approaches is that arrhythmias are problematic even if the blood pressure is fine.  There have been situations where I had to put together a continuing education course on blood pressure and pulse and the correct assessment of both.  That was a long time before the recent article on common mistakes made by medical students in these measurements.

If measurements that are considered routine and done hundreds of times a day are problematic what about observations that occur on the other end of the spectrum.  A common health care myth today is: "If I have a checklist and check off all of the boxes on that list that will lead me to some kind of diagnosis."   That is probably a minimization of the myth.  In the case of psychiatry, the myth is more: "If I convert a standard psychiatric assessment into a form (or a checklist) - the ultimate product of going through that list will basically be a psychiatric evaluation and diagnosis."  Systems of care who use this approach can deny these myths as much as they want but I see this happening every day. Organized psychiatry and the DSM approach to diagnostic criteria is partially responsible, although the manual does say that it can't be used by anybody.  It doesn't say who specifically should use it and it does not suggest (like Kendler) that it is an indexing approach.

Looking at the graphic at the top of the page illustrates why a form or a checklist does not suffice.  The observer/psychiatrist in the drawing is doing more than asking the subject a series of yes or no questions.  The psychiatrist is looking for patterns in symptoms (medical and psychiatric), what is happening in relationships with the person (including the relationship to the psychiatrist), and the person's conscious state - specifically whether there has been a departure from baseline.  There is often a balance between historical detail, phenomenology, the person's ability to describe what has happened and a plausible scenario based on probability estimates from the psychiatrist's previous experience.  Any psychiatrist who has been trained in many presentations of complex psychiatric illness is more likely to see those patterns than somebody who has not been.

To illustrate some of these concepts I will describe several cases that are all what non-psychiatrists (nonphysicians and other physicians) called hysteria. Hysteria is an old word that dies hard.  The DSM equivalent is histrionic personality disorder.  The generic use of the term suggests a person who is overly emotional, dramatic and attention seeking but there are 8 diagnostic criteria that are unchanged between DSM-IV and DSM-5.  Many clinicians opt for the term Cluster B - a DSM-IV originated term that grouped personality disorders in groups according to some common diagnostic features.  The Cluster B group included individuals that often appear dramatic, emotional, or erratic.  Those personality disorder diagnoses include antisocial, histrionic, narcissistic, and borderline.

The rule-in criteria (significant impact on life circumstances and onset when you expect a personality disorder to occur) and the rule-out criteria (not due to another mental or physical disorder) are predictable for any causal reader of a DSM and could be included on any checklist or form.  How does all of that play out?  Well here are a few examples:

Hysterical patient #1:   A 30 year old woman presents for a therapy intake.  She is mumbling and laughing.  The therapist describes her as "odd and having an odd affect."  She alludes to some suicidal behavior in the past but is smiling and joking about it.  The therapist has the impression that she is manipulative and overly dramatic.  He contacts the clinic psychiatrist and says that she is histrionic but he is concerned about her suicide potential.  The psychiatrist sees her that day and makes a diagnosis of bipolar disorder-mixed type with psychotic features.  The patient is eventually stabilized on lithium and an atypical antipsychotic.

Hysterical patient #2:  A 25 year old woman is being treated on a general medicine ward for dehydration from a respiratory infection.  She suddenly gets tearful and agitated.  Family members visiting have to physically restrain her when when she tries to get out of bed.  She starts to make very loud high pitched vocalizations.  A psychiatrist is called to go in to assess hysteria and possibly sedate the patient.  The psychiatrist sees an agitated young woman who is not able to respond coherently to any examination questions.  Brief neurological examination suggests increased intracranial pressure is the problem and the patient requires immediate transfer to a neurological intensive care unit. 

Hysterical patient #3:  A 58 year old man is referred acutely from a therapist for acute panic attacks and "probable Cluster B" personality traits.  He has recently retired due to osteoarthritis of the knees.  He had no earlier history of panic attacks but the therapist thought that he was overly dramatic at the initial session 2 days earlier when he was unable to relax and breathe normally with behavioral techniques that are usually effective.  The psychiatrist gets a history of the patient needing to abort an exercise stress test two weeks earlier due to the arthritis and having  a prolonged period of immobility at home due to sore knees. During that time he developed acute shortness of breath.  The episodes of anxiety that he described were secondary to shortness of breath and not panic attacks.  The psychiatrist sends the patient to the emergency department where an acute pulmonary embolism is diagnosed and he is admitted to the ICU.     

These are just a few examples restricted to one collection of psychiatric symptoms that illustrates what my colleague was referring to.  The value of psychiatric training goes far beyond what is in the DSM and what checklists and templates can be extracted from it.  I have never really met a psychiatrist who was focused on the DSM probably because it is implicitly evident to us that it is an index more than a diagnostic manual. We are focused on what is not in the DSM and as far as I know that is not well documented in many places.  Those are the patterns associated with clinical practice and that should have been gleaned along the way with medical training.  The DSM doesn't tell you how a pulmonary embolism presents. It is possible that you night have never seen one. But in medical training I can guarantee that it was discussed somewhere along the line in the differential diagnosis of dyspnea.  I can guarantee that one of those attendings discussed the phenomenon of the healthy young adult immobilized by air travel who gets off at their destination and suddenly has an acute pulmonary embolism. All of those features and urgencies should be in a physicians conscious state when they are seeing the whole patient and not some DSM/checklist version of a patient.

This brief post also illustrates the biasing effects of language.  What  does "Cluster B" really mean?  Aren't people who are acutely medically (or psychiatrically) ill dramatic, emotional, or erratic?  Hysteria is an extremely biasing term that over the centuries has been applied selectively to women rather than men.   The examples above illustrate that point.  If you are seeing the world through DSM language and that is your only lens - you are by definition not seeing the whole patient.  The list of possible errors in that landscape is very large.

There are a number of constraints that will get  in the way of a trained psychiatrist trying to see the whole patient.  Inadequate time is one, but time frames vary significantly.  Diagnosing a life threatening medical problem upon seeing a patient may take a matter of minutes and is clearly the most important diagnosis.  Seeing a long series of new patients briefly to prescribe treatment will necessarily mean that certain features in the above diagram will be missed.  So-called measurement based care depending on a large number of checklists to "quantitate" affects or other psychiatric states makes the same mistake.  Collaborative care where a psychiatrist looks at these rating scales and recommends treatments makes the same mistake.

The best assurance that the critical aspects of care will not be missed is to be sitting across the room from someone who has been taught all of the critical aspects of care.  That process is complex and as far as I know has never been adequately described.  A first approximation is whether that person knows what they are seeing and how to respond.

George Dawson, MD, DFAPA     

Pattern Matching in Psychiatric Diagnosis

I first heard about pattern matching and the importance it has in medical diagnosis over 30 years ago.  A friend of mine who was in medical school at the time told me about one of his professors who was always interested in the Augenblick diagnosis or the diagnosis that  could be arrived at in the blink of an eye.  He gave me examples of several diagnoses that could be either made immediately or within minutes based on a set of features that would lead to immediate associations in the mind of the clinician without an extensive evaluation.

I had many encounters in my medical training with the same phenomenon.  I can recall being on the Infectious Disease consult team and being asked to see a patient with ascites for the possible diagnosis and treatment of spontaneous bacterial peritonitis.  The consultant with an expert in Streptococcal infections and after patiently listening to the resident's presentation he asked what we thought of the rash on the patient's leg.  The patient had lower extremity edema with a slightly erythematous hue and a slight exudate in areas.  What was the diagnosis?  Without skipping a beat the consultant said this was streptococcal cellulitis and suggested sending a sample to the lab for confirmation.  It was subsequently confirmed and treated.  Why was the attending physician able to hone in on and diagnose this rash when it escaped the detection of two Medicine residents and two medical students?  He was an Infectious Disease specialist and that may have biased him in that direction but is there something else?

One of the ways that physicians and probably all classes of diagnosticians arrive at Augenblick diagnoses or efficiently clump and sort through larger amounts of information faster is by pattern matching.  Pattern matching is also the reason why clinical training is necessary to become an adequate diagnostician.  That will not happen with rote learning alone.  It is one thing to read about heart sounds and actually experience them and to have that skill refined by listening to hundreds and thousands of normal hearts and hearts with varying degrees of pathology.  Rashes are classic examples and several studies have documented that the speed and accuracy with which dermatologists can make an accurate diagnosis of a rash is much higher than the average physician.  In pattern matching a recognizable feature of the patient's illness triggers an immediate association with the physicians experiences from the past leading to a facilitated diagnosis.

Probably the best conceptualizations of pattern matching comes from the fields of philosophy and cognitive science.  My favorite author is Andy Clarke and his book Microcognition.  He addresses the issue of biologically relevant cognitive science and the model of parallel distributed processing.  A simplified diagram drawn from this model is shown below:

In this case we have a very practical problem of a patient with known bipolar disorder and a question of whether or not they have had a stroke.  In this case the respective clouds (there are many more) represent collection of features of medical diagnoses that may be relevant to the case.  Unlike a textbook, these features represent a lot of varied information including actual events and nonverbal information like the clinicians past history of diagnosing strokes and caring for people who have had strokes.   Each cloud here can contain hundreds or tens of thousands of these features.  These features are unique aspects of the clinician conscious state and the only way to control for variability between clinicians is to assure that physicians in the same speciality have similar exposure to these experiences in their training.  Even in the ideal situation where all specialists have an identical exposure to the same illness there will be variability based on different levels of ability and other capacities.  An example would be a Medicine resident I worked with whose examination of the heart with a stethoscope predicted the echocardiogram results.  It became kind of a joke on our team at the time that all he had to do was hold his stethoscope in the air in a patient's room and it was as good as an ultrasound.

The basic idea in pattern matching is that the clinician immediately recognizes one of the features they know and that allows for a rapid diagnosis or plan based on that feature.   Looking how that works in the hypothetical case we can look at a few features in the map:

 For the purpose of this discussion consider that our patient B is a 60 year old woman with a 35 year history of known bipolar disorder.  She has known her psychiatrist for years.  One day the husband calls with the concern that the patient seems to have developed a problem with communication.  She seems to be talking in her usual voice but he can't comprehend what she is saying.  She does not appear to be manic or depressed.  The psychiatrist listens to the patient on the phone and concludes that she has a fluent aphasia and recommends that they take her to the emergency department as soon as possible.  Ongoing care requires that the psychiatrist talk with the emergency department physician and hospitalist to make sure that acute stroke is high in their differential diagnosis and eventually go in to the hospital and examine the patient to confirm the diagnosis.

Practically all cases of psychiatric diagnosis require some measure of this pattern matching process with varying degrees of medical acuity.  I would go so far to suggest that it is the most important aspect of the diagnosis.  Keep in mind that the pattern matching also applies to the purely psychiatric part of the diagram.  Despite all of the recent criticism and focus on the DSM 5 the elaboration of pattern matching leads us to several important conclusions:

1.  Psychiatric diagnosis is a much more dynamic process than rote learning from a diagnostic manual.  The average clinician should have many more features of diagnoses than are listed in any manual.

2.  Psychiatric diagnosis requires medical training.  There is no way that our psychiatrist in the example could have made the diagnosis of aphasia and remain involved in the diagnostic process to its conclusion without medical training and previous exposures to these scenarios.

3.  The training implications of these scenarios are not often made explicit.  Every medical student, resident and practicing physician needs to be exposed to a diverse population of patients with problems in their area of expertise in order to develop a pattern matching capability.  They can also benefit by asking attending clinicians about how they made rapid diagnoses, but at that level of training the question is not obvious.

4.  Removing physicians with these capabilities from the diagnostic loop reduces the capability of that loop.  The best example I can continue to think of is the primary care process where the diagnosis and ongoing treatment of depression or anxiety depends on the results of a checklist that the patient completes in less than 5 minutes.  This assumes that there is an entity out there called depression that is based purely on a verbal description and pattern matching is not required.  It actually assumes that there is a population of people with this affliction.  Despite all of the hype about how this is "measurement based care" - I don't think that a single person like that exists.

5.  Pattern matching blurs the line between objective and subjective.  There is often much confusion about this line.  Are there "objective criteria" that can be written in a manual somewhere that captures even the basic essence of diagnosing a stroke in a patient with bipolar disorder?  Is there an "objective" checklist out there somewhere that can capture the problem?  Obviously not.  For some reason people tend to equate "subjective" with "bad" or "unscientific".  In the example given and any similar example, the subjective state with the most experience diagnosing strokes is probably the "best" diagnostician - subjective or not.  An "objective" rating scale doesn't stand a chance.

So consider pattern matching to be an important but unspoken part of the diagnostic process.  For obvious reasons it is more important than diagnostic criteria in a manual.  The most obvious of these reasons is that you really cannot practice medicine without it.

George Dawson, MD, DFAPA

Clark A.  Microcognition.  London, A Bradford Book, 1991.