DO Diagnostic Reasoning and Evidence-Based Medicine

Question 1

Bayes' theorem in clinical medicine states that the post-test probability of disease depends on which two factors?

Accepted Answer

Pre-test probability and test likelihood ratio

Answer

Sensitivity and specificity alone

Answer

Patient age and symptom duration

Answer

Sample size and confidence interval

Question 2

When a test has high specificity, a positive result is most useful for:

Accepted Answer

Ruling IN disease (SpPin)

Answer

Ruling OUT disease

Answer

Determining treatment dosage

Answer

Confirming prognosis

Question 3

A 55-year-old male smoker presents with hemoptysis and a new lung mass on CXR. The pre-test probability for lung cancer is estimated at 60%. The CT-guided biopsy has a sensitivity of 95% and specificity of 99%. A positive biopsy result essentially:

Accepted Answer

Confirms the diagnosis (very high post-test probability)

Answer

Still requires additional testing before treatment

Answer

Is insufficient without PET scan correlation

Answer

Reduces the probability of malignancy

Question 4

Which statistical measure describes the strength of association between an exposure and outcome in a case-control study?

Accepted Answer

Odds ratio (OR)

Answer

Relative risk (RR)

Answer

Hazard ratio (HR)

Answer

Number needed to harm (NNH)

Question 5

Confirmation bias in clinical diagnosis refers to:

Accepted Answer

Seeking information that confirms an initial diagnosis while ignoring contradictory evidence

Answer

Overestimating the prevalence of rare diseases

Answer

Using recent memorable cases to guide diagnosis

Answer

Anchoring on the first piece of diagnostic information

Question 6

A 95% confidence interval (CI) for a relative risk that does NOT cross 1.0 indicates:

Accepted Answer

The result is statistically significant at the p < 0.05 level

Answer

The result is clinically irrelevant

Answer

The study had insufficient power

Answer

The effect size is too small to matter