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