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CLINICAL REASONINGIN GENERAL PRACTICE
Dr Charles Todd
OBJECTIVES
At the end of the session you should:• Understand cognitive methods utilised in
making a diagnosis• Recognise some of the special features that
apply in general practice • Have a strengthened ability to reach an
accurate diagnosis in the general practice consultation
• Understand how and why errors in reasoning occur
KEY MESSAGE:STOP & THINK!
Remember this antismoking slogan? Plus message spray painted over it…
THINK FIRST -
MOST DOCTORS DON’T SMOKE
Smoke first –Most doctors
don’t think!
WHY IMPORTANT?
Diagnostic errors:
i.Common: estimates 10-20%.
ii.Among medical errors are the second leading cause of adverse effects (after medication errors)
iii.Associated with high morbidity.
iv.The most common and most costly source of malpractice payments (in UK & USA).
GENERAL PRACTICE CONSULTATIONS
• Short• Enormously varied• Problems undifferentiated• Serious disease uncommon• Multiple tasks: the key one is to establish
the reasons for the patient’s attendance – with new problems this means reaching a diagnosis
MAKING A DIAGNOSIS
• Key competency for GPs• Forms the basis for determining the patient’s
treatment, prognosis, etc • Concerns moving “backwards” from the patient’s
complaints (the illness) to the disease (target disorder)
• Important to consider physical, social and psychological aspects
• The history is critical – examination and investigations play a relatively small role
KAHNEMAN’S SYSTEMSOF THINKING
• System 1 operates automatically and quickly, with little effort
• System 2 involves effortful mental activity
• While most of the time system 1 is in operation, system 2 can to some extent overrule it
• We can “toggle” between the two
CLINICAL PROBLEM SOLVING IN PRACTICE
What methods are used in reaching a diagnosis?
1) Intuition2) Hypothesis generation and testing3) Follow a structured guideline or
algorithm
INTUITION
• Instant realisation that the presenting signs and symptoms conform to an already known pattern
• Reflex rather than reflective
• Applies where the presentations is very familiar
• “Pattern recognition”
• Kahneman’s System 1
HYPOTHETICO-DEDUCTIVE METHOD
• Analytical approach• Laboured, time-consuming• Kahneman’s System 2• Ideas are generated during the interview about
what the underlying problem is• These “hypotheses” are then tested and
refined by further questions, examination and investigations
MORE ON HYPOTHESES
• Hypotheses are “explanatory ideas” that are increasingly refined through the consultation
• The first are generated very early on in history taking (within seconds)
• Usual strategy followed is to “prove” rather than refute a particular hypothesis
• Used by clinicians of all types – more experienced are better at it
GENERATING HYPOTHESES
Consider:• Probability or likelihood of a given
condition in a specific setting• Potential seriousness and • Treatability
of any possible diagnosis – especially with regard to the value of early detection
WHEN THE GOING GETS TOUGH
• Consider broad categories first, e.g. think about what system is involved
• Keep an open mind
• Look for a unifying diagnosis
• Utilise checklists as aide-memoires
• Avoid fishing expeditions
• Listen to the patient and think!
CHECKLISTSSystem-based Pathological Anatomical
Cardiovascular Congenital Skin
Respiratory Acquired Muscle
Gastrointestinal - Traumatic Bone
Genitourinary - Infective Pleura
Neurological - Inflammatory Lungs
Psychological - Metabolic Heart
etc etc etc
SOURCES OF ERROR AND BIAS• Jumping to conclusions and fixing on them – being “blind” to other
ideas• Basing diagnosis on recall of a similar case from the past or novelty,
rather than awareness of epidemiology in the setting• Continuing reference to existing and/or extension of existing diagnostic
label• Unquestioning faith in diagnostic labels applied by others, especially
consultants• Failure to reassess when things don’t fit with what is expected
• Being distracted by too much information• Focus on ruling in rather than ruling in
ERROR AND BIAS (ctd)• Confirmation bias: focus on ruling in rather than refuting a
particular diagnosis (i.e. only seeking evidence to confirm)
• Over-reliance on results of investigations
• “Colluding” with the patient who is asking for reassurance
• Multiple doctors involved failure to see the bigger picture
• Emotional factors / denial
• Being too tired or rushed
• Lack of knowledge and experience
EXAMPLES FROM PRIMARY CARE SIGNIFICANT EVENTS
Presentation Initial diagnosis Eventual diagnosis Reason for error
60 yr old rectal bleeding
Haemorrhoids Rectal cancer InexperienceFailure to follow guidelines
2 yr old unwell with fever, unusual blanching rash
Viral infection Meningococcal septicaemia
“Blindness” and collusion
40 yr old obese type 2 DM with severe recurrent vertigo
Labyrinthitis Cerebellar stroke Multiple doctorsFailure to reassess
COMMUNICATION SKILLS FOR BETTER DIAGNOSIS
• Listen – and show it• Don’t interrupt (“the golden minute”)• Ask open-ended questions first, then more
directed ones• Be receptive to all verbal and non-verbal
cues• Summarise and check• Be open to the patient’s perspective (ICE)
SPECIAL CONSIDERATIONS IN GENERAL PRACTICE
• Be pragmatic and action oriented
• Use time judiciously
• Don’t trust specialists uncritically
• Learn to live with uncertainty
• Manage risk
• Identify and respond to the patient’s ideas about what is wrong
USE OF CLINICAL EPIDEMIOLOGY TO IMPROVE DIAGNOSTIC
ACCURACY• Statistical methods are underutilised in
reaching a diagnosis
• Estimate initial probability of disease (prevalence in the setting)
• Know specificity and sensitivity of diagnostic tests
• Refine probability based on strength of evidence (“likelihood ratio”)
FINAL TIPS• Generate more than one possible diagnositic idea• Think of the worst thing this could be• Don’t just focus on presenting symptoms: review
recent consultations and look at bigger picture• Always be ready to reconsider or ask a colleague• Listen to your gut, but• Never abandon your critical faculties
READINGSackett D, Haynes et al. Clinical Epidemiology. A Basic
Science for Clinical Medicine. Little Brown
Elstein A, Schwarz A. Clinical problem solving and diagnostic decision making... BMJ 2002; 324: 729-732
http://healthland.time.com/2013/04/24/diagnostic-errors-are-more-common-and-harmful-for-patients/
Scott I. Errors in clinical reasoning: causes and remedial strategies. BMJ 2009; 339: 22-25
Fraser R. Clinical Method: a general practice approach. Butterworth Heinemann.
Kahneman D. Thinking, Fast and Slow. Penguin, 2012