Wrestling with risk
4 Things
• You are not a diagnostician
• You are a risky doctor
• You get lucky (a lot)
• Diagnosis can be dangerous
You are not a
diagnostician
How sure are you?
• 98-100%
• 95-98%
• 90-95%
• 85-90%
• <85%
Cardiologists
Sens 79.9%
Spec 86.3%
 Sensitivity=a/a+c
 Specificity=d/d+b
Truth table and calculations
705 patients in ED
129/705 had AMI
Sens 96.9%
Spec 54.7%
 Sensitivity 97%
 Specificity 54%
H-FAB in AMI
125125
44
261261
315315
H-H-
FABPFABP
 What does a +ve test
result mean?
 What does a -ve test result
mean?
What answers do we really
get from a Truth table?
...
H-FAB testing for AMI
• A +ve test means they have
the diagnosis
• A +ve test means they
probably have the diagnosis
• A +...
• Medicine is a science of
uncertainty and an art of
probability.
You are a
‘probablistician’
risky
doctors
Radiopaedia
What’s an acceptable
level of risk?
CC: http://www.flickr.com/photos/warrenski/283620129/
1:50
1:25
1:10
Example - PERC rule
• Age>49
• Pulse>100
• Pulse Ox<95%
• Current haemoptysis
• Oestrogen use
• Previous venous thromboemb...
1:50
1:25
1:10
Pre test probability for PE
6.9 % pre test probability of PE.
PERC Rule
sens = 97.4%
spec = 21.9%
PERC Rule
sens = 97.4%
spec = 21.9%
6.9 % pre test
probability of PE.
21.9% negative
• Gestalt plus PERC rule will fail to spot two
PEs for every thousand patients
investigated.
• You get lucky (a lot)
Radiation Fear Bleeding
Did you miss the big one?
• are we happy???
• Gestalt plus PERC rule will fail to spot two
PEs for every thousand patients
investigated.
does a ‘miss’ matter?
QuickTime™ and a
decompressor
are needed to see this picture.
What does a miss really
mean?
Multi-step sequence
needed for harm to
take place
Diagnosis missedDiagnosis missed
They don’t comeThey don’t come
backback
It gets worseIt gets worse
The treatmentThe treat...
• Probabalistic
• Risky
• Lucky
• Multi step sequence for harm
http://emcrit.org/misc/imaging-in-pe-diagram/
Just for fun
http://emcrit.org/misc/imaging-in-pe-diagram/
Just for fun
Is this all about PE?
• Good problem solving, sound judgement and
effective clinical decision making are
considered the highest attributes of ph...
Only when disclosure of uncertainty
becomes commonplace in medical practice
will the physician/patient relationship evolve...
4 Things
• You are not a diagnostician
• You are a risky doctor
• You get lucky (a lot)
• The dangers of diagnosis
4 Things
• You make probability assessments
• You take risks (but you understand them)
• Even when you miss, you usually g...
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
Sdc smacc wrestling with risk
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  • General question as ice breaker Common reasons likely to be labels, prognosis, therapy. Ultimately because it is useful to know. BUT the key to a rational diagnostician is that it should be beneficial for the patient and not just the physician
  • 55 year old man with 2 hour hx of chest pain. no risk factors. previously fit and well
  • Digivote slide Answer is 90-95%
  • Digivote LR +ve 2.138 LR -ve 0.057
  • So as a clinician we have no idea whether our patient has the right diagnosis or not. We just know that they probably do or they probably don’t. Even with tests that have a high sensitivity.
  • Howard Atwood Kelly (February 20, 1858 – January 12, 1943) was an American gynecolo gist . He was one of the &quot;Big Four&quot; founding professors at Johns Hopkins Hospit al . [1] (The &quot;Big Four&quot; were William Osler , Professor of Medicine; Will iam Stewart H alsted , Professor of Surgery; Howard A . Kelly, Professor of G ynecology; and William H. Welch , Professor of Pathology.) Kelly is credited with establishing gynecology as a true specialty. [2] Harvey Williams Cushing , M.D. (April 8, 1869 - October 7, 1939), was an American neurosurgeon and a pioneer of brain su rger y, and the first to describe Cushing&apos;s syndrome . [1] He i s often call ed the &quot;father of modern neuro surge ry. Thayer prof medicine at John Hoplins
  • Point 1 you are not a diagnostician
  • Point 2 is that..... Probability So if we accept that we have a probability issue then we have a problem of risk.
  • chest pain tests.
  • Digivote
  • 1666 ?PE patients in 13 US and NZ EDs Gestalt plus PERC gives the following PERC Rule sens = 97.4% spec = 21.9% Designed with acceptable miss rate of 2% Even in this study PEs were missed. ^ Kline, JA; Courtney, DM; Kabrhel, C; Moore, CL; Smithline, HA; Plewa, MC; Richman, PB; O&apos;Neil, BJ et al (2008). &quot;Prospective multicenter evaluation of the pulmonary embolism rule-out criteria&quot; . Journal of Thrombosis and Haemostasis 6 (5): 772–780. doi : 10.1111/j.1538-7836.2008.02944.x . PMID   18318689 .
  • Digivote
  • 6.9 % pre test probability of PE. Kline study multicentre 8138 patients gestalt plus PERC
  • Point 3
  • Sequence has to be completefor harm to occur IN appendicitis. Miss diagnosis, not come back early, not get recognised, not get to theatre, not respond to treatment, not survive.
  • Sequence has to be complete for harm to occur IN appendicitis. Miss diagnosis, not come back early, not get recognised, not get to theatre, not respond to treatment, not survive.
  • So what have we established thus far?
  • Monty hall Game Show - let’s make a deal in the 70s
  • headache low risk chest pain dvt/vte appendicitis bacterial infections in children meningitis
  • Sdc smacc wrestling with risk

    1. 1. Wrestling with risk
    2. 2. 4 Things • You are not a diagnostician • You are a risky doctor • You get lucky (a lot) • Diagnosis can be dangerous
    3. 3. You are not a diagnostician
    4. 4. How sure are you? • 98-100% • 95-98% • 90-95% • 85-90% • <85%
    5. 5. Cardiologists Sens 79.9% Spec 86.3%
    6. 6.  Sensitivity=a/a+c  Specificity=d/d+b Truth table and calculations
    7. 7. 705 patients in ED 129/705 had AMI Sens 96.9% Spec 54.7%
    8. 8.  Sensitivity 97%  Specificity 54% H-FAB in AMI 125125 44 261261 315315 H-H- FABPFABP
    9. 9.  What does a +ve test result mean?  What does a -ve test result mean? What answers do we really get from a Truth table? 125125 44 261261 315315 H-H- FABPFABP
    10. 10. H-FAB testing for AMI • A +ve test means they have the diagnosis • A +ve test means they probably have the diagnosis • A +ve test means they are more likely to have the diagnosis than before I did the test 125125 44 261261 315315 H-H- FABPFABP
    11. 11. • Medicine is a science of uncertainty and an art of probability.
    12. 12. You are a ‘probablistician’
    13. 13. risky doctors
    14. 14. Radiopaedia
    15. 15. What’s an acceptable level of risk? CC: http://www.flickr.com/photos/warrenski/283620129/
    16. 16. 1:50 1:25 1:10
    17. 17. Example - PERC rule • Age>49 • Pulse>100 • Pulse Ox<95% • Current haemoptysis • Oestrogen use • Previous venous thromboembolism • Recent surgery • Unilateral leg swelling PERC Rule sens = 97.4% spec = 21.9% ^ Kline, JA; et al (2008). "Prospective multicenter evaluation of the pulmonary embolism rule-out criteria". Journal of Thrombosis and Haemostasis 6 (5): 772–780.
    18. 18. 1:50 1:25 1:10
    19. 19. Pre test probability for PE 6.9 % pre test probability of PE.
    20. 20. PERC Rule sens = 97.4% spec = 21.9%
    21. 21. PERC Rule sens = 97.4% spec = 21.9% 6.9 % pre test probability of PE.
    22. 22. 21.9% negative
    23. 23. • Gestalt plus PERC rule will fail to spot two PEs for every thousand patients investigated.
    24. 24. • You get lucky (a lot)
    25. 25. Radiation Fear Bleeding
    26. 26. Did you miss the big one?
    27. 27. • are we happy??? • Gestalt plus PERC rule will fail to spot two PEs for every thousand patients investigated.
    28. 28. does a ‘miss’ matter?
    29. 29. QuickTime™ and a decompressor are needed to see this picture. What does a miss really mean?
    30. 30. Multi-step sequence needed for harm to take place
    31. 31. Diagnosis missedDiagnosis missed They don’t comeThey don’t come backback It gets worseIt gets worse The treatmentThe treatment does not workdoes not work Harm takes placeHarm takes place They get betterThey get better anywayanyway They do comeThey do come backback The treatmentThe treatment worksworks Significant harmSignificant harm avoidedavoided Diagnosis madeDiagnosis made ..but the diagnosis is..but the diagnosis is missed again!missed again!
    32. 32. • Probabalistic • Risky • Lucky • Multi step sequence for harm
    33. 33. http://emcrit.org/misc/imaging-in-pe-diagram/ Just for fun
    34. 34. http://emcrit.org/misc/imaging-in-pe-diagram/ Just for fun
    35. 35. Is this all about PE?
    36. 36. • Good problem solving, sound judgement and effective clinical decision making are considered the highest attributes of physicians. The theory and practice of clinical decision making Croskerry P. Can J Anaesth 2005;52:1-8
    37. 37. Only when disclosure of uncertainty becomes commonplace in medical practice will the physician/patient relationship evolve to a level of greater understanding and satisfaction for both the physician and patient.
    38. 38. 4 Things • You are not a diagnostician • You are a risky doctor • You get lucky (a lot) • The dangers of diagnosis
    39. 39. 4 Things • You make probability assessments • You take risks (but you understand them) • Even when you miss, you usually get lucky • Pursuing a diagnosis is not always right

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