Renumeration - The Manitoba College of Family Physicians

Renumeration
Numeracy for Family Doctors
Roger Suss MD CCFP(EM) FCFP
Dept of Fam Med
University of Manitoba
Conflict of interest
None to declare
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Objectives
1. To convince doctors that numbers are
essential to their job
2. Which numbers?
3. Where can you find them?
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Siberian shaman c. 1900
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Lord Kelvin 1883 on science and math
‘When you can measure what you are
speaking about, and express it in
numbers, you know something about it;
but when you cannot express it in
numbers, your knowledge is of a meagre
and unsatisfactory kind; it may be the
beginning of knowledge, but you have
scarcely, in your thoughts, advanced to
the stage of science, whatever the matter
may be.’
‘Do not imagine that mathematics is
hard and crabbed, and repulsive to
common sense. It is merely the
[abstraction] of common sense.’
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Should this
woman take
this pill?
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How Much?
Harms
Benefits
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How Much?
Harms
Benefits
Harms
Benefits
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Which is the better question?
What should I do?
How much will this help?
(How much? Of what?)
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Which is the better question?
What is the diagnosis?
(And what is the treatment that
goes with that diagnosis?)
What is the prognosis?
(And can I improve on that?)
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Case 1
50 year old woman otherwise well.
What should I do?
What is the diagnosis?
(And treatment for that
diagnosis?)
How much will this help?
What is the prognosis?
(And can I improve on
that?)
Picture from we-fix-u.com
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Ferri's Clinical Advisor 2014
What should I do?
Watchful waiting is an acceptable option … because many warts
will disappear without intervention over time.
General Rx
•Common warts:
Liquid nitrogen and electrocautery are also common
methods of removal. Cure rates for cryotherapy are 50% to
70% after three to four treatments.
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Ferri's Clinical Advisor 2014
How much will this help?
Watchful waiting is an acceptable option … because many warts
will disappear without intervention over time. How many? In
how long?
General Rx
•Common warts:
○Liquid nitrogen and electrocautery are also common
methods of removal. Cure rates for cryotherapy are 50% to
70% after three to four treatments. Compared to what?
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Treatment of Warts
How much? Of what?
• Spontaneous resolution by 2 years is 78%
• Cryotherapy.
– NNT not statistically significant
– NNH (pain) almost 1
•
Cochrane Review 2012
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Case 2
• 50 year old woman previously well.
• 7 days ago started to get runny nose and
cough. Was starting to improve but then:
• Yesterday fever 38.1 C, bloody yellow red
nasal discharge, and bilateral cheek pain.
• What is her diagnosis?
• What is her prognosis?
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Prognosis without tx = 80% resolution in 14 days
Clinical cure at 7-14 days
NNT = 10-205
Diarrhea
NNH = 5-14
Dynamed
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Case 3
• 50 year old woman comes back to discuss her
recent cholesterol results. She does not
smoke, or drink. She tries to eat a healthy diet,
and runs 2 miles every day. She is otherwise
healthy. Her father had an MI at age 59.
• Her BP is 120/75.
• Her Total Cholesterol is 6, HDL is 1, and LDL 4.
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CCS Guidelines 2014
Modified Framingham Risk Score
14.6% risk of cardiovascular disease in 10 years
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therapeuticseducation.org
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Which Numbers?
• Prognosis without treatment for my patient
• How effective is the Tx? RRR
• How effective will the treatment be in my
patient? ARR = 1/NNT
• Number Needed to Harm NNH
• Confidence Interval (not the p value)
• Likelihood Ratios (Sensitivity and Specificity)
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RESULTS
Among the 530 infants in the intention-to-treat population who initially had negative
results on the skin-prick test, the prevalence of peanut allergy at 60 months of
age was 13.7% in the avoidance group and 1.9% in the consumption group
(P<0.001). Among the 98 participants in the intention-to-treat population who
initially had positive test results, the prevalence of peanut allergy was 35.3% in
the avoidance group and 10.6% in the consumption group (P=0.004).
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CER 13.7% - EER 1.9% = ARR 11.8% aka NNT 10
(CER 13.7% - EER 1.9%)/CER 13.7% = RRR 86%
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CER 35.3% - EER 10.6% = ARR 24.7% aka NNT 4
(CER 35.3% - EER 10.6%)/CER 35.3% = RRR 70%
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Potential Objections
•
•
•
•
The math is too difficult for family doctors
The answers are too unclear
The numbers are not easily available
Some patients really want to “do something”
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No benefit -------------------------- Benefit
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No benefit -------------------------- Benefit
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Conclusions
What should I do?
How much? Of what?
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Ready to learn more?
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Where to look for quick answers:
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DynaMed
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CTFPHC
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theNNT.com
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NNT = 16 ?how long?
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Wrong answers
•
•
•
•
•
•
•
You should…
Standard of Care is…
Is beneficial…
Your patient deserves…
More doctors recommend…
The guidelines say…
Most effective treatment…
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•
•
•
•
•
•
•
You should…
Standard of Care is…
Is beneficial…
Your patient deserves…
More doctors recommend…
The guidelines say…
Most effective treatment…
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More wrong answers
•
•
•
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Improves serum levels by X %
Prevents medical procedures by Y %
Improves patient satisfaction by Z %
Statistically significant
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•
•
•
•
Improves serum levels by X%
Prevents medical procedures by Y%
Improves patient satisfaction by Z %
Statistically significant
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How Much? Of What?
NNH
NNT
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How Much? Of What?
Forest plots
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Forest plots
1. Effect Size
2. Uncertainty due to
random factors
3. Uncertainty due to
uncontrolled
variables - bias
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Likelihood ratios
LRpos = sensitivity / (1 - specificity)
LRneg = (1 - sensitivity) / specificity
Sensitivity = TP/(TP+FN)
Specificity = TN/(FP+TN)
Case 1 RLQ pain
A 29-year-old patient presents to your office with abdominal
pain and a fever. The patient was well until 1 day ago and had
never experienced abdominal pain. A vague periumbilical pain
awoke him from sleep 12 hours previously, and he soon
developed anorexia, nausea, and vomiting. His wife consulted
their family medical reference guide and then brought him to
the office, concerned that his symptoms matched a
description of appendicitis. The pain then migrated to the
right lower quadrant (RLQ) and was much worse while he was
riding in the car to the physician's office.
The patient's oral temperature is 37.8°C; the pulse rate and
blood pressure are normal. He has RLQ tenderness, guarding
but not rigidity, or rebound tenderness in the RLQ. A rectal
examination reveals no tenderness, and he does not exhibit
the psoas or obturator signs. Rovsing sign is positive.
JAMA Rational Clinical Exam series
Case 1 RLQ pain
Prevalence in pts in ER
<60 years old ~20%
LR+ 8
LR+ 4
LR+ 3
LR+ 2.8
LR- 0.6
Using the parameters
above what is his
probability of having
appendicitis?
~93%
The Last End
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