Clinical Decision Making Flashcards
What is the decision-making bias heuristic called “Availability?”
Overestimating the probability of unusual events because of recent or memorable instances.
e.g. The last patient I saw with a headache had a brain tumor so I will do a CT scan on everyone with headache
Source of recent “chagrin”
What is the decision making bias heuristic called “Representatitveness”
Overestimating rare disease by matching patients to “typical picture” of that disease–ignoring pre-test probabilities.
“When you hear hoofbeats think horses not zebras.”
What is the decision making bias heuristic called “Anchoring?”
Fail to adjust probability of a disease or outcome based on new information akin to “premature closure.”
“I was told in sighout the patient has X, so I will not reconsider the diagnosis even in light of conflicting evidence.”
What is value-induced decision making bias heuristic?
Overestimate probability of an outcome based on value associated with that outcome.
“It would be horrible to miss a brain tumor in this patient so we should get a CT on this healthy patient with headache.”
Define narrative definition of sensitivity:
Given patient has the disease, what is the likelihood of positive test? P(T+/D+)
Remember Sensitive and Specificity are “Given you know Disease status” (a test characteristic but not clinically useful)
Define narrative definition of specificity:
Given patient does not have disease, what is likelihood of negative test? P(T-/D-)
Remember Sensitive and Specificity are “Given you know Disease status” (a test characteristic but not clinically useful)
Define Relative Risk
P (disease/exposure) / P(disease/no exposure)
What is Prospect Theory?
“Bird in the hand is worth 2 in the bush”
People will avoid gambles if the outcome is viewed as a gain. People will seek gambles if the outcome is viewed as a loss. Take a bigger risk to avoid pain.
What is “Primacy”
First impressions stick.
Suzy is smart, good in school, and she is poorly behaved. = Good view of Suzy
Suzy is poorly behaved, and she is smart, good in school. = Poor view of Suzy
How do create Probability from Odds?
probability = # of desirable outcomes
# of possible outcomes
odds = # of desirable outcomes
# of undesirable outcomes
Odds of heads on coin toss = 1:1
Probability = 1/2
If Odds are 1:3
Probability = 1/4 = .25
If P(.25), then Odds = .25/(1-.25) = 1:3
What is Positive Likelihood rations and how do you use them? If you want to determine post-test probability from LR, what do use need to use.
+LR = (TPR)/(FPR) = Sensitivity / 1-specificity
Post-Test Odds = Pre-test odds * +LR
Fagan Nomogram allows you determine post-test probability from pre-test probability (prevalence) and LR+
How do you calculate absolute risk reduction and number needed to treat.
What is Hazard Ratio?
ARR = Control Event Rate(CER) - Experimental Event Rate (EER)
NNT = 1/ARR
Hazard Ratio = Relative Risk = EER/CER
Bates theorem for P(D|T+
=(sens)(prevalence)/ (Sens)(prev) + (1-spec)(1-Prev)
Define Liklihood ratios in terms of sensitivty and and specificty/
\+LR = sensitivty/1-specificity -LR = 1-sensitivity/specificty
High likelihood ratios (e.g., LR>10) indicate that the test, sign or symptom can be used to rule in the disease, while low likelihood ratios (e.g., LR<0.1) can rule out the disease. Likelihood ratios of around 1 indicate that no useful information for ruling the diagnosis in or out has been produced from the clinical findings.
