Probabilistic Approach in Medicine
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Questions and Answers

In what scenario is the probabilistic approach most suitable?

  • When statistical thinking is not required.
  • When false positives or negatives are common. (correct)
  • When results must be 100% accurate.
  • When immediate decisions are needed.

What is the initial step in the probabilistic approach?

  • Pretest probability estimation (correct)
  • Diagnostic testing.
  • Performing an ECG
  • Post-test probability calculation

What does prevalence refer to in the context of probability estimation?

  • The accuracy of a diagnostic test.
  • The characteristics of a disease.
  • The frequency of a disease in a population. (correct)
  • The use of cognitive heuristics.

What is a true positive (TP) in diagnostic testing?

<p>Correctly identifying an individual with a disease. (D)</p> Signup and view all the answers

What is a key characteristic of clinical decision-making in medicine?

<p>Inherent uncertainty due to imperfect data. (D)</p> Signup and view all the answers

Why is understanding probability important in clinical decision-support systems?

<p>It is crucial for updating information and making informed decisions. (B)</p> Signup and view all the answers

What is a false negative (FN) in diagnostic testing?

<p>Identifying a diseased individual as healthy. (D)</p> Signup and view all the answers

According to the content, what is the true positive rate of the HIV PCR test?

<p>98% (D)</p> Signup and view all the answers

What influences probability estimation?

<p>How easily similar cases come to mind. (A)</p> Signup and view all the answers

What is the true negative rate of the HIV PCR test?

<p>99% (D)</p> Signup and view all the answers

In the case study, what condition does Ms. Kamala have?

<p>Coronary artery disease (D)</p> Signup and view all the answers

What previous medical intervention has Ms. Kamala undergone related to her condition?

<p>Two coronary artery bypass graft surgeries (D)</p> Signup and view all the answers

What risk does Ms. Kamala face if she avoids a third surgery, according to the case study?

<p>A high risk of a fatal heart attack (B)</p> Signup and view all the answers

Medical decisions based on probabilities are described as:

<p>Necessary but also perilous (C)</p> Signup and view all the answers

What does sensitivity (TPR) measure?

<p>Probability that a diseased patient tests positive (A)</p> Signup and view all the answers

Which formula represents specificity (TNR)?

<p>TN / (TN + FP) (B)</p> Signup and view all the answers

What does a higher ROC curve indicate?

<p>Better test performance (C)</p> Signup and view all the answers

What happens to specificity and sensitivity when you increase the cutoff value?

<p>Higher specificity, lower sensitivity (C)</p> Signup and view all the answers

What is the consequence of a false positive result?

<p>A non-diseased patient receives a positive result. (C)</p> Signup and view all the answers

For serious diseases where effective treatment exists, what should be minimized?

<p>False Negatives (FNs) (C)</p> Signup and view all the answers

Which of the following describes the false negative rate (FNR)?

<p>Probability a diseased patient receives a negative result. (D)</p> Signup and view all the answers

What is plotted on the axes of a Receiver Operating Characteristic (ROC) curve?

<p>Sensitivity vs. 1 - Specificity (D)</p> Signup and view all the answers

What is the primary concern when deciding whether to treat a patient for deep vein thrombosis (DVT)?

<p>Balancing the risk of pulmonary embolism against the risk of bleeding from anticoagulants. (C)</p> Signup and view all the answers

In medicine, ambiguous language can lead to what?

<p>Potential miscommunication in medical decision-making. (B)</p> Signup and view all the answers

What is the first step in the hypothetico-deductive approach to diagnosis?

<p>Data Collection. (B)</p> Signup and view all the answers

What does the probabilistic approach use to update the likelihood of a disease?

<p>Bayes’ theorem. (B)</p> Signup and view all the answers

In the hypothetico-deductive approach, what is generated based on initial data?

<p>List of possible diagnoses. (A)</p> Signup and view all the answers

What is the purpose of diagnostic tests in the hypothetico-deductive approach?

<p>To confirm or rule out diagnoses. (A)</p> Signup and view all the answers

In the probabilistic approach, what two things does a doctor consider before confirming a diagnosis after a positive test result?

<p>Test accuracy and disease prevalence. (A)</p> Signup and view all the answers

What can probability and decision analysis provide in complex medical situations?

<p>Clearer guidance. (A)</p> Signup and view all the answers

What is the clinician's initial action in the probabilistic approach?

<p>Estimating the pretest probability. (D)</p> Signup and view all the answers

What serves as an anchor for probability estimation in objective probability estimates?

<p>Prevalence of the disease in a population. (D)</p> Signup and view all the answers

What is the outcome of a True Negative (TN) result?

<p>Correctly identifying a healthy individual as healthy. (D)</p> Signup and view all the answers

What is the main challenge caused by overlapping distributions of biological measurements?

<p>Misclassification of individuals. (A)</p> Signup and view all the answers

In the context of probability estimation, what cognitive heuristic may influence a clinician's judgment?

<p>How easily similar cases come to mind. (A)</p> Signup and view all the answers

What does refining probability estimates by placing patients into subgroups with known disease probabilities improve?

<p>Objective Probability Estimates (D)</p> Signup and view all the answers

Under what conditions is the probabilistic approach most beneficial?

<p>In situations where false positives or negatives are common. (C)</p> Signup and view all the answers

What is the implication of a False Positive (FP) test result?

<p>A healthy individual is incorrectly identified as diseased. (E)</p> Signup and view all the answers

What is the primary concern when deciding whether to treat Ms. Kirk for deep vein thrombosis (DVT)?

<p>Balancing the risk of pulmonary embolism against bleeding complications. (B)</p> Signup and view all the answers

In the hypothetico-deductive approach, what is the purpose of collecting patient history and symptoms?

<p>To gather initial data for hypothesis generation. (A)</p> Signup and view all the answers

What is the initial step in the hypothetico-deductive approach to diagnosis?

<p>Data collection through observation and history-taking. (D)</p> Signup and view all the answers

What does probability and decision analysis aim to provide in complex medical situations?

<p>Clearer guidance (B)</p> Signup and view all the answers

How does the probabilistic approach update the likelihood of a disease?

<p>Using probability theory based on test results. (D)</p> Signup and view all the answers

In the probabilistic approach, what does a doctor consider after a positive test result?

<p>Test accuracy (sensitivity/specificity) and disease prevalence. (A)</p> Signup and view all the answers

What is generated based on initial data in the hypothetico-deductive approach?

<p>A list of possible diagnoses (differential diagnosis). (B)</p> Signup and view all the answers

What is the formula for calculating sensitivity (TPR)?

<p>TP / (TP + FN) (D)</p> Signup and view all the answers

Which of the following describes specificity (TNR)?

<p>Probability that a non-diseased patient tests negative (A)</p> Signup and view all the answers

What is a key reason why clinical decision-making is often uncertain?

<p>Imperfect data and unpredictable treatment outcomes. (A)</p> Signup and view all the answers

What does the False Negative Rate (FNR) represent?

<p>Probability that a diseased patient receives a negative result (A)</p> Signup and view all the answers

What is the importance of understanding probability in clinical decision-support systems?

<p>It is crucial for updating beliefs with new information. (C)</p> Signup and view all the answers

What is the formula for calculating specificity (TNR)?

<p>TN / (TN + FP) (D)</p> Signup and view all the answers

What happens to specificity when you increase the cutoff value?

<p>Specificity increases (D)</p> Signup and view all the answers

What is Ms. Kamala's medical history significant for in the case study?

<p>She has undergone two coronary artery bypass graft (CABG) surgeries. (D)</p> Signup and view all the answers

What is the major risk Ms. Kamala faces if she decides to avoid a third surgery?

<p>A high risk of a fatal heart attack due to oxygen deprivation. (A)</p> Signup and view all the answers

What should be minimized for serious diseases where effective treatment exists?

<p>False negatives (FNs) (D)</p> Signup and view all the answers

According to Smith L., what statement describes medical decisions based on probabilities?

<p>They are necessary but also perilous. (C)</p> Signup and view all the answers

What is plotted on the ROC curve?

<p>Sensitivity (TPR) vs. 1 - Specificity (FPR) (A)</p> Signup and view all the answers

What is the true positive rate of the HIV PCR test mentioned?

<p>98% (C)</p> Signup and view all the answers

What does the provided information say about medical decisions relying on associations between symptoms and diseases?

<p>They lead to uncertainty. (C)</p> Signup and view all the answers

Which of the following describes sensitivity (TPR)?

<p>Probability that a diseased patient tests positive (C)</p> Signup and view all the answers

What is the core reason for uncertainty in medical decision-making?

<p>Imperfect data and unpredictable treatment outcomes. (A)</p> Signup and view all the answers

What is the formula for specificity (TNR)?

<p>TN / (TN + FP) (C)</p> Signup and view all the answers

According to the content, what is crucial for clinical decision-support systems?

<p>Understanding and updating probability with new information. (C)</p> Signup and view all the answers

What makes probabilistic reasoning a valuable approach in medical decisions?

<p>It handles uncertainty effectively. (B)</p> Signup and view all the answers

What condition does Ms. Kamala have?

<p>Coronary artery disease (A)</p> Signup and view all the answers

What type of surgeries has Ms. Kamala already undergone?

<p>Coronary artery bypass graft (CABG) (A)</p> Signup and view all the answers

If Ms. Kamala avoids the third surgery, what primary risk does she face?

<p>A high risk of a fatal heart attack. (B)</p> Signup and view all the answers

What is a significant challenge in medical decision-making?

<p>Medical decisions rely on imperfect associations. (B)</p> Signup and view all the answers

What can be said about associations between symptoms and diseases?

<p>Medical decisions rely on imperfect associations between symptoms and diseases. (A)</p> Signup and view all the answers

What is the primary concern when deciding whether to treat Ms. Kirk for a possible DVT?

<p>Balancing the risk of pulmonary embolism against the risk of bleeding from treatment. (C)</p> Signup and view all the answers

In the hypothetico-deductive approach, what is the purpose of ordering diagnostic tests?

<p>To confirm or rule out possible diagnoses. (D)</p> Signup and view all the answers

What is the first step in the hypothetico-deductive approach?

<p>Data collection through observation and history-taking. (B)</p> Signup and view all the answers

In the probabilistic approach, what does a doctor consider alongside test accuracy when interpreting a positive test result?

<p>The prevalence of the disease in the patient's population. (B)</p> Signup and view all the answers

What is the purpose of generating a differential diagnosis in the hypothetico-deductive approach?

<p>To list all possible diagnoses based on initial data. (D)</p> Signup and view all the answers

What is a potential consequence of using ambiguous language when describing a patient's condition?

<p>Potential miscommunication in medical decision-making. (A)</p> Signup and view all the answers

What is the next step after diagnostic testing in the hypothetico-deductive approach?

<p>Final diagnosis and treatment decision (B)</p> Signup and view all the answers

In the probabilistic approach, what is the purpose of diagnostic testing?

<p>To reduce uncertainty and update disease probability. (B)</p> Signup and view all the answers

What is a clinician's initial step in the probabilistic approach?

<p>Estimating pretest probability. (B)</p> Signup and view all the answers

In the treatment of Ms. Kirk, what is weighed against the risk of excessive bleeding from anticoagulants?

<p>The risk of a fatal pulmonary embolism from an untreated clot. (B)</p> Signup and view all the answers

Which approach uses probability theory to update the likelihood of a disease based on test results?

<p>The probabilistic approach (A)</p> Signup and view all the answers

What serves as an anchor for objective probability estimates?

<p>Prevalence of the disease. (A)</p> Signup and view all the answers

Why do distributions of biological measurements often overlap?

<p>Because normal and diseased individuals can have similar results. (D)</p> Signup and view all the answers

What step comes after diagnostic testing in the probabilistic approach?

<p>Post-test probability calculation. (C)</p> Signup and view all the answers

What influences subjective probability estimation?

<p>How much the patient resembles a mental image of the disease and how easily similar cases come to mind. (C)</p> Signup and view all the answers

What is a false positive (FP) result?

<p>A test indicating disease when the patient is healthy. (D)</p> Signup and view all the answers

What is the estimated pretest probability of heart disease for the 60-year-old man with chest pain?

<p>50% (A)</p> Signup and view all the answers

Flashcards

Medical Decision-Making (MDM)

The branch of medicine focused on making decisions under conditions of uncertainty, using probability to guide choices.

Uncertainty in Medicine

Uncertainty arises from incomplete data and unpredictable treatment outcomes, making clinical decisions complex.

Probabilistic Reasoning

Using probability to assess the likelihood of different outcomes and updating these probabilities with new information.

True Positive Rate

The likelihood that a test correctly identifies those with the condition.

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True Negative Rate

The likelihood that a test correctly identifies those without the condition.

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Pretest Probability

The probability of a patient having a disease before a test result is known.

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Imperfect Associations

Medical decisions are based on connections that are not perfect between symptoms and diseases, leading to uncertainty.

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Necessity and Peril

Even the best doctors make mistakes sometimes because medical decisions are based on probabilities.

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Probability in Medicine

Using probability and decision analysis to guide complex medical decisions.

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Ms. Kirk's case

A 33-year-old woman with a history of blood clots, now experiencing leg pain and swelling.

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Diagnostic Uncertainty (DVT)

Uncertainty whether a new blood clot is present, despite abnormal blood flow in ultrasound.

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DVT Treatment Dilemma

Balancing the risk of a fatal pulmonary embolism from an untreated clot against bleeding risks from anticoagulants.

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Ambiguous Medical Language

Terms like 'probable' cause miscommunication in medical decisions.

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Probability-Based Expressions

Using probabilities to improve clarity when describing likelihoods of diseases and treatment outcomes.

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Hypothetico-Deductive Approach

A diagnostic approach involving data collection, hypothesis generation, hypothesis testing and determining a diagnosis.

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Probabilistic Approach (Diagnosis)

Uses probability to update likelihood of disease based on test results and prior probability (Bayes' theorem).

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Sensitivity (TPR)

Probability that a diseased patient tests positive.

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Specificity (TNR)

Probability that a non-diseased patient tests negative.

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False Negative Rate (FNR)

Probability that a diseased patient receives a negative result.

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False Positive Rate (FPR)

Probability that a non-diseased patient receives a positive result.

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Increasing the cutoff

Higher specificity, lower sensitivity.

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Lowering the cutoff

Higher sensitivity, lower specificity.

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Serious diseases, effective treatment

Minimize false negatives (increase sensitivity).

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ROC Curve

Plots sensitivity vs. 1 - specificity across different cutoffs to show test performance.

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Diagnostic Testing

Using tests to decrease uncertainty and refine disease probability.

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Post-Test Probability

Updating disease probability after test results using methods like Bayes' theorem.

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Subjective Probability

Estimating probability based on resemblance to a typical disease case.

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Objective Probability

Estimating probability using disease prevalence in a population.

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True Positive (TP)

A test says "diseased" when the person truly is diseased.

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True Negative (TN)

A test correctly says "healthy" when the person truly is healthy.

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False Positive (FP)

A test says "diseased" when the person is actually healthy.

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Hypothetico-Deductive Method

Systematically gathering patient info, creating possible diagnoses, ordering tests, and deciding on treatment.

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Probabilistic Diagnosis

Using probability to adjust disease likelihood based on test results, taking base rates into account.

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Bayes' Theorem Application

Using evidence to update the chance of a disease.

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Data Collection (Diagnosis)

The initial step in diagnosis; gathering history, symptoms, and examination findings.

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Hypothesis Generation

Making educated guesses (differential diagnosis list) based on initial patient information.

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Probabilistic Medical Reasoning

A valuable method for handling uncertainty in medical decisions, especially when the data isn't perfect.

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HIV PCR Test Accuracy

The probability of a donor actually having HIV given a positive or negative test result.

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Ms.Kamala's Decision Dilemma

Undergo a third operation with higher surgical risk and lower success rate, or avoid surgery and face a high risk of a fatal heart attack due to oxygen deprivation in her heart muscle?

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Pretest Probability Estimation

Initial assessment estimating the chance of disease based on symptoms and medical history.

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Subjective Probability Estimation

Using personal judgment and experience affects probability assessment.

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Availability Heuristic

Probability assessment affected by how easily similar cases come to mind.

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Objective Probability Estimates

Using prevalence (disease frequency) in a population as a basis for probability.

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False Negative (FN)

False negative (FN) refers to a test indicating no condition when one actually exists.

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Overlapping Distributions

The distributions that healthy individuals results overlap with the distributions of diseased individual results.

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Minimize FNs

Serious diseases where effective treatments exist need to minimize which kind of result?

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Minimize FPs:

When the test is used for less serious diseases or risky treatments, which errors should we reduce?

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Better Test Performance

What does a higher ROC curve indicate?

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ROC Curve plotting

A graph plotting sensitivity vs. 1-specificity across different cutoff values.

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Sensitivity (TPR) formula

Probability that a diseased patient tests positive. (TP / (TP + FN))

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Specificity (TNR) formula

Probability that a non-diseased patient tests negative. (TN / (TN + FP))

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Test Cutoff value

The cutoff point affects test sensitivity and specificity.

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Less serious diseases

Minimize false positives (FPs).

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Higher ROC curve

Test B has better ability to accurately identify and differentiate between those with and without the condition.

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Uncertainty in MDM

Clinical decision-making involves inherent uncertainties due to imperfect data and unpredictable outcomes.

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Probabilistic Reasoning Value

Handling uncertainty in clinical decisions, though not suitable for all cases.

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HIV PCR True Positive Rate

The PCR test is positive 98% of the time when HIV antibody is present.

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HIV PCR True Negative Rate

The PCR test is negative 99% of the time when HIV antibody is absent.

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Necessity and Risk

Medical decisions based on the probabilities are necessary but also have risk.

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Ms. Kirk's Presentation

A situation where a patient has pain and swelling in their leg, possibly indicating a blood clot.

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Diagnostic Imprecision (DVT)

Uncertainty in diagnosis, despite initial tests showing abnormalities, further tests might be needed.

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Treatment Dilemma

The challenge of deciding whether to treat a possible blood clot due to the risks associated with treatment.

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Probability Expressions

Using precise numbers to describe medical possibilities.

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Ambiguous Medical Terms

Vague terms used by clinicians that can lead to misunderstandings.

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Diagnostic Approach

Gathering patient info to form and assess possible diagnoses.

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Hypothesis Formation

Generating a list of possible diagnoses after initial data gathering.

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Hypothesis Examination

Ordering tests to either validate or rule out potential diagnoses.

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Diagnosis & Treatment Choice

Deciding on the most likely diagnosis, and planning a treatment.

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Bayes' Theorem Use Case

Applying probability to diagnosis, especially when false results are common.

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Cognitive Heuristics (Probability)

Thinking influenced by judging similarity to typical disease presentation.

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Prevalence-Based Probability

Using disease frequency in a population as a base for probability estimates.

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Post-Test Probability Calculation

Calculating probabilities and updating them after new tests.

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