94 Questions
What is the purpose of illness scripts?
To facilitate differential diagnosis
What is the definition of prevalence?
The number of people in a given time period in a certain population
What is the purpose of physical exams in the diagnostic process?
To gather more information
What is the best estimate of disease probability before a test is conducted?
Pretest probability
Which of the following is true about likelihood ratios?
They are used to determine the diagnostic usefulness of a test.
What does a likelihood ratio less than 1 indicate?
The test decreases the probability.
What is the purpose of creating a problem list in the process of differential diagnosis?
To gather information about the patient's signs and symptoms
What is the availability heuristic in the differential diagnosis process?
Cognitive bias or mental shortcut that individuals use when making judgments or decisions
When should clinicians start considering differential diagnoses?
After gathering some information about the chief concern
What is the equation for calculating the positive likelihood ratio (LR+)?
LR+ = (1 - Specificity) / Sensitivity
What is the equation for calculating the negative likelihood ratio (LR-)?
LR- = Specificity / (1 - Sensitivity)
What do you need to be careful of when applying multiple LR's?
To avoid double-counting and to account for closely correlated findings.
What is the significance of pathognomonic findings?
Pathognomonic findings strongly increase the probability of a condition.
What is the equation for calculating the positive likelihood ratio (LR+)?
LR+ = 1−Specificity/Sensitivity
What is the purpose of the differential diagnosis process?
The purpose of the differential diagnosis process is for clinicians to consider multiple possible causes of a patient's signs and symptoms before making a final diagnosis.
What are the potential errors that can occur during the differential diagnosis process?
The potential errors that can occur during the differential diagnosis process include: first guess being usually wrong, missing a serious diagnosis by focusing on common conditions, and being subject to availability heuristic and recall bias.
What factors should be considered when generating a differential diagnosis?
When generating a differential diagnosis, factors such as probability (what is most likely), prognosis (must-not-miss conditions), and pragmatism (conditions with best benefit to harm ratio if treated) should be considered.
What are the steps involved in the process of differential diagnosis?
The steps involved in the process of differential diagnosis include: creating a problem list based on gathered information, creating a processes problem list using scientific language, and creating a table with differential diagnoses considering epidemiology, timing, syndrome/symptoms, and mechanism.
What is the purpose of history-taking in the diagnostic process?
History-taking is important in the diagnostic process as it provides valuable information about the patient's symptoms, medical history, and other relevant factors. It helps in understanding the patient's perspective, identifying potential causes of the symptoms, and guiding further investigations.
What are illness scripts and how do they aid in the diagnostic process?
Illness scripts are patterns and organized mental summaries of a clinician's knowledge of a disease. They include information about predisposing conditions, clinical features, and the mechanism of illness. Illness scripts aid in the diagnostic process by helping clinicians learn, compare and contrast conditions, and facilitate differential diagnosis.
What is a differential diagnosis and why is it important?
A differential diagnosis is a list of conditions that are potential candidates for explaining a patient's concerns. It is important because it helps clinicians consider multiple possibilities and avoid premature closure on a single diagnosis. It allows for a comprehensive evaluation of different conditions and ensures appropriate management and treatment.
What is the significance of physical exams in the diagnostic process?
Physical exams play a crucial role in the diagnostic process as they involve the clinician inspecting, auscultating, percussing, and palpating the patient. These exams help in identifying signs of disease that can be perceived by the clinician. By assessing the patient's physical findings, clinicians can gather additional information to support or refute a diagnosis, guide further investigations, and monitor the patient's response to treatment.
A naturopathic doctor has just obtained some initial information from a patient about her main concern. What is the next step?
Consider what information is still needed
If a practitioner is seeking to obtain valuable medical information while exposing the patient to minimal harm, discomfort or inconvenience, what aspect of the diagnostic process will they engage in?
History taking
In what section of a medical chart would we be most likely to include information about symptoms?
Subjective
What term is used to describe a mental summary of a practitioner's knowledge of a disease?
Illness script
What single attribute of a test will best help a practitioner determine its value as evidence as it relates to a particular condition?
Likelihood ratio
How might illness scripts most help in creating a differential diagnosis?
A patient's illness script is compared with different disease illness scripts
When comparing disease illness scripts, which of the following should you do?
Create a table with illness scripts in adjacent columns or rows
Obsessive compulsive disorder typically begins before age 25. This information is part of what illness script component?
Epidemiology
A patient complains of a headache that started with mild pain this morning and has been getting worse over the course of the day with no periods of relief. How would the timing best be described?
Acute, progressive
A portion of a syndrome statement in a patient illness scripts reads as follows: "unilateral headaches with phonophobia". What might the patient have indicated during the intake?
Their head hurts on the left side and they find that sounds make it worse
What is the purpose of gathering some information about the patient's chief concern before considering a differential diagnosis?
More effective comparison with your disease illness scripts
A naturopathic student intern reads a book whose central thesis is that a condition which is thought to be rare is in fact common. If they are not careful, which cognitive bias may worsen their diagnostic performance as a result?
The availability heuristic
How should one proceed from the beginning of the encounter through the development of a differential diagnosis?
Obtain some information from the patient; create a problem representation and patient illness script; compare the patient illness script to a number of disease illness scripts
An intern proposes a diagnosis for one of their patients because "the symptoms all fit". What might the intern have failed to consider that would most help create a strong list of differentials?
Which conditions are most likely, which are most serious, and which are most amenable to treatment
What is the main value of differential diagnosis?
It helps to avoid excessive certainty about an initial hypothesis
According to the majority of research discussed in class, a number of cognitive biases are consistent with what error(s) when estimating probability in medicine?
Overestimation of disease probability both before tests are administered and after the results of testing are received
An intern completes a patient intake and is convinced that the patient they've seen has a rare disease, because "the symptoms match perfectly!" What should the intern's supervisor be most concerned that the intern is doing?
Substituting judgments of how similar a disease is to the stereotypical presentation of that disease for judgments of the probability of disease
You are discussing a patient case with your colleagues at the teaching clinic and voice uncertainty about the probability that your patient with joint pain has Disease X
Ariana points out that patients with joint pain are diagnosed with Disease X 14% of the time in a primary care setting Bradley mentions that 60-70% of patients with Disease X have joint pain similar to what your patient described to you Carla claims that the prevalence of Disease X in Canada is 1-2% of the population, according to recent statistics Danaka adds that government statistics on the lifetime prevalence of Disease X in Canadians is 30% Assuming all of them are correct, which is the best to use for a pretest probability?
14%
A patient describes her headaches as "all over" her head. They are accompanied by nausea and occasional vomiting which can occur first thing in the morning. She has been feeling tired lately and has been making more mistakes at work.
Thinking of differentials, you consider the following facts:
These are some of the classic symptoms of a brain tumor Headaches occur in about 50% of patients with brain tumors Cognitive dysfunction occurs in about 35% of patients with brain tumors In general practice, one study found that 0.1% of people presenting with headache had primary brain tumors Which option is closest to the most reasonable pretest probability that this patient has a brain tumor?
1%
Which of the following would make for the best reference class for use in estimating a pretest probability?
Research on the eventual diagnosis a group of patients received after presenting with a complaint similar to your patient's
You are investigating the evidence involved in the diagnosis of infectious mononucleosis. You find the following data:
Finding LR+ LR- splenomegaly 7.0 0.94 any cervical adenopathy 2.1 0.22 posterior cervical adenopathy 3.1 0.69 headache 1.3 0.73 Which of the following combinations of findings should you avoid applying (i.e. you should apply evidence from only one of the findings)?
Any cervical adenopathy and posterior cervical adenopathy
You are reading an article about the diagnosis of infectious mononucleosis and see the following likelihood ratios:
7.0 0.94 0.3 0.03 Which LR represents the minimum information you would need to move your estimate of the probability from approximately 10% to less than 1%?
0.03
With which pretest probability would your estimate of the probability change the most If you applied evidence with an LR of 5?
50%
A naturopathic doctor claims that the treatment they recommend for CIN 1 (a condition where there are slightly abnormal cervical cells) is effective. They say that 75% of the women they treat who have CIN 1 find that their condition resolves. Before deciding how persuasive this evidence should be, what further piece of information would be most important to consider?
How often women find that their CIN 1 resolves without this intervention
You are looking for diagnostic evidence in the literature and are having difficulty finding likelihood ratios. What should you look for in order to be able to calculate likelihood ratios?
Sensitivity and specificity
A ____________ is a manifestation of disease reported by a patient. It is considered ___________
____________ focuses on patients’ ideas and feelings about illness and impact on life (fears, expectations)
A ________ is to learn, compare and contrast conditions where as a __________ facilitates differential diagnosis
A ___________ is a list of conditions that are candidates for explaining patient’s concerns
What is a premature close?
failing to consider reasonable alternatives after initial diagnosis is made
___________ new occurrences of a condition in a specific population over a given period
__________________ probability below which the diagnosis is so unlikely it is excluded without further testing
___________ describes the probability above which the diagnosis is so likely you would treat the patient without further testing
A _____________ is a manifestation of a disease that the clinician perceives (see, hear, feel, etc.). It is considered ______
A red flag is a ________________________
What are the four main categories included in an illness script?
epidemiology timing signs and symptoms (clinical presentation) mechanism/pathophysiology
After making your simple problem list, you would want to make a ___________
____________ is a way to obtain information from a patient and compare this information to one’s understanding of different conditions to generate multiple hypotheses
Most _____________ not typically the most serious and consequences of missing a serious diagnosis are higher
_____________ are particularly subject to the availability heuristic
________________ is a cognitive bias or mental shortcut that individuals use when making judgments or decisions
What are the three main things to consider in a differential diagnosis? (three P's)
o Probability: what is most likely? o Prognosis: “must-not-miss” conditions; conditions that are most serious if left unconsidered o Pragmatism: what conditions have the best benefit to harm ratio if treated
___________ is what conditions have the best benefit to harm ratio if treated
_______________ is how likely something is usually on a scale of 0-100%
Respondents _______________ the probability of a diagnosis before and after testing
___________ is consistent with cognitive biases, including base rate neglect, anchoring bias and confirmation bias
___________ is a human trait; substitute judgments of representativeness for judgments of actual probability
_______________ describes the degree to which something is representative of, or similar to, the stereotype
An uncommon presentation of a _______________ is more likely than a common presentation of a _________________
What is a pretest probability?
Best reference class is the __________________________
A basic reference class uses the _________________________________
What are the cons to using a basic reference class?
• May be an underestimate if it’s something that people frequently seek medical attention for • Less helpful for acute conditions
______________________ refers to studies that give eventual diagnosis in patients presenting with complaints similar to your patient’s
What are the pros to using a specific reference class?
• Take presenting symptom into account • Considers that people tend to seek medical attention for some conditions more than others
What are the two things you should NOT use for reference classes?
Both A and B
______________ is a number representing the diagnostic usefulness of a test
What is the general written equation for LR?
Probability that you would see some evidence if your hypothesis were true/probability that you would see the exact same evidence if your hypothesis was false
Describe what it means if LR = 1
useless
Describe what it means if LR >1
increases probability
Describe what it means if LR < 1
decreases probability
A positive LR means that the finding was ____________
A negative LR means the finding was __________
____________________ considers patients who have the disease, the probability that the test will be positive; probability that you would see certain evidence if your hypothesis was true
_________ considers patients who do not have the disease, the probability that your test will be negative; complement probability that you would see the same evidence if your hypothesis were false
For ______________ pretest probabilities, you can increase your pretest probability by a certain % based on the LR
For _________________ pretest probabilities, you can multiply the probability by ____________ to get an estimate
A positive predictive value (PPV) is the probability that a disease is ______________________
A negative predictive value (NPV) is the probability that disease is ________________________
What are pathognomonic findings?
pathognomonic findings are findings that if present, strongly increases the probability of a condition
_____________ are findings which if absent, strongly decreases the probability of a condition
What are the four main errors that occur in practice when applying evidence?
o Fail to recognize the need for more evidence (premature closure) o Poorly chosen or missed test (question, physical exam, lab, etc.) o Incorrectly performed test o Incorrect interpretation (ex. lack of knowledge, bias)
Test your knowledge on probability and its role in decision-making. Explore the concept of overestimating probabilities and its impact on medical diagnoses. Learn about cognitive biases such as base rate neglect and confirmation bias. Discover how overestimation can lead to medication overuse and excessive procedures. Take this quiz to enhance your understanding of probability and its practical implications.
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