Doctors May Guess Your Diagnosis and Why They May Be Wrong

This thread is all about heuristic clinical reasoning which means a doctor's mental shortcuts to come to a diagnosis. Heuristic is defined in Wikipedia as:

Heuristic (/hjʉˈrɪstɨk/; Greek: "Εὑρίσκω", "find" or "discover") refers to experience-based techniques for problem solving, learning, and discovery that give a solution which is not guaranteed to be optimal. Where the exhaustive search is impractical, heuristic methods are used to speed up the process of finding a satisfactory solution via mental shortcuts to ease the cognitive load of making a decision. Examples of this method include using a rule of thumb, an educated guess, an intuitive judgment, stereotyping, or common sense.

In more precise terms, heuristics are strategies using readily accessible, though loosely applicable, information to control problem solving in human beings and machines.

In medical practice there may be many reasons which encourage heuristic clinical reasoning such as emergent medical situations or general lack of time for detailed history taking and examinations, lack of resources including an important resource would be a patient who was able to give a medical history or a knowledgeable surrogate. Another factor promoting such reasoning is the expense or potential health hazard to the patient from a procedure which would be appropriate for a definite diagnosis. Finally,  physicians who are not fully educated in a particular specialty may be unaware of all the different diagnoses which are available to consider. Unfortunately, for some physicians heuristic reasoning tends to become a relied upon habit. 

There are a number of categories classifying the types of reasoning which can make up heuristic clinical reasoning.  I found an interesting list by the CanadianAssociation of Emergency Physicians (CAEP).

Here is a list of categories and the description of each by the CAEP:

1. ANCHORING-Focusing on vivid, salient features in a clinical presentation early in the diagnostic process and failing to adjust this first impression later as more information becomes available.

2. ASCERNMENT BIAS-When thinking is unduly influenced by prior expectations (e.g. stereotyping or gender-bias).

3. AVAILABILITY-Options appear more likely when they are readily brought to mind (e.g. a subacrachnoid hemorrhage diagnosis is given more consideration on the differential for headache if it was seen in a case a week ago.)

4. COMMISSION BIAS-The idea that something always needs to be done to the patient instead of letting things take their course--more common in confident physicians; things get done that were unnecessary.

5. CONFIRMATION BIAS-Looking for things to support your diagnosis/hypothesis rather than looking for disconfirming evidence (which is usually a more effective strategy).

6. CONTRAST EFFECT-When interpretation of a particular case is influenced by adjacent cases--even though they are independent of each other.)

7. DIAGNOSES MOMENTUM-When diagnoses gather momentum without gathering evidence.

8. FUNDAMENTAL ATTRIBUTION ERROR- Judging and blaming particular patients (e.g. obese, borderline personality disorder, addicted patients) for their illnesses by focusing on their disposition (character, personality, intelligence) rather than considering their situational circumstances (socio-economic, upbringing, history of physical/sexual abuse).

9. HINDSIGHT BIAS- Learning from past experience is hindsight. However hindsight bias occurs when, knowing the outcome, people either make themselves look good or look bad, thereby distorting any chance of realistic learning.

10. OMISSION BIAS- The tendency toward inaction and non-intervention.  Error arises from things not getting done that should have been done.

11. OVERCONFIDENCE-The general belief that we are better than we really are--a misplaced belief that affects one's thoughts and actions.

12. PLAYING THE ODDS also known as FREQUENCY GAMBLING- is the tendency in equivocal or ambiguous situations to opt for a benign diagnosis on the basis that it is significant more likely than a serious one.

13. PREMATURE CLOSURE-Shutting off thinking before there is sufficient evidence to suggest a particular diagnosis--when the diagnosis is made the thinking stops.

14. REPRESENTATIVENESS RESTRAINT- We tend to look for prototypical manifestations of disease--atypical presentations are more likely to get missed.

15. SEARCH SATISFICING- reflects the universal tendency to call off a search once something is found. Co-morbidities, second foreign bodies, other fractures and co-ingestants in poisoning all might be missed.

16. VISCERAL BIAS- when emotions overly intrude into decision-making.  Countertransference may result in feeling unduly negative or positive toward patients leading to suboptimal decisions regarding diagnosis and management.

17. YIN-YANG OUT-The outlook that once patients have been worked up the Yin-Yang  further effort will be futile.

18. ZEBRA RETREAT- Backing away from a rare diagnosis for reasons other than it being rare: thinking that you will attract a reputation of being esoteric, unrealistic  or a wastrel of resources or time.

19. TRIAGE CUEING- deals with Emergency Room triage: the tendency to inherit the abbreviated thinking that occurred at triage (patients  seen in the minor area are considered as only having minor complaints).

and finally

BLIND SPOT BIAS, a general belief that people have that they are less susceptible to bias than others. 

As you see, there can be many ways that heuristic clinical reasoning can go wrong.  And yet, doctors will use this reasoning as part of the beginning to form a diagnosis when rushed or a diagnosis still not firmly established at the time that some prompt treatment for physical support is critical. But the "guess" has the many limitations as noted above.  So what is most important is that all doctors should be aware that they are at the time practicing heuristic reasoning and should know the details of what potential errors of reasoning can occur by such use and thus use with caution.

Have you ever heard your doctor tell you: "I am just guessing that you have..."? And how did or would you respond? ..Maurice. 

Graphic: From Google Images-Alfred Nobel (1833-1896)