OCC OCC Evidence-Based Medicine & Research 1 — Questions and Answers
Question 1: Which type of study provides the highest level of evidence in evidence-based medicine hierarchy?
- Systematic review and meta-analysis of randomized controlled trials (Correct answer)
- Individual randomized controlled trial
- Prospective cohort study
- Expert opinion and case series
Correct answer: Systematic review and meta-analysis of randomized controlled trials
Systematic reviews and meta-analyses pooling data from multiple high-quality RCTs sit at the top of the evidence hierarchy.
Question 2: In a randomized controlled trial (RCT), what is the purpose of blinding participants and investigators?
- To reduce performance and detection bias (Correct answer)
- To improve patient recruitment
- To reduce cost of the study
- To ensure equal randomization
Correct answer: To reduce performance and detection bias
Blinding prevents performance bias (participants changing behavior) and detection bias (investigators interpreting outcomes differently) when they know the treatment assignment.
Question 3: A study reports a relative risk (RR) of 0.6 for a new drug compared to placebo for MI. What does this mean?
- The drug reduces MI risk by 40% relative to placebo (Correct answer)
- The drug reduces MI risk to 0.6 per 1000 patients
- The drug increases MI risk by 40%
- The drug has a 60% absolute risk reduction
Correct answer: The drug reduces MI risk by 40% relative to placebo
RR of 0.6 means the treated group has 60% of the risk of the control group — a 40% relative risk reduction.
Question 4: What is the number needed to treat (NNT) if the absolute risk reduction (ARR) of a treatment is 5%?
- 20 (Correct answer)
- 5
- 0.05
- 100
Correct answer: 20
NNT = 1/ARR = 1/0.05 = 20, meaning 20 patients need to be treated for 1 additional patient to benefit.
Question 5: In a diagnostic test evaluation, a test with high sensitivity is best used for which purpose?
- Screening (ruling out disease when negative) (Correct answer)
- Confirming disease when positive
- Staging disease severity
- Monitoring treatment response
Correct answer: Screening (ruling out disease when negative)
A highly sensitive test has few false negatives — a negative result effectively rules out disease (SnNout: Sensitive test, Negative result = rule Out).
Question 6: Which statistical measure describes the probability that a patient without the disease will test negative on a diagnostic test?
- Specificity (Correct answer)
- Sensitivity
- Positive predictive value
- Negative predictive value
Correct answer: Specificity
Specificity = true negatives / (true negatives + false positives) — it is the probability that a disease-free person tests negative.
OCC OCC Evidence-Based Medicine & Research 1
Which type of study provides the highest level of evidence in evidence-based medicine hierarchy?