PEBC Drug Information and Literature Evaluation — Questions and Answers
Question 1: A pharmacist is evaluating a randomized controlled trial (RCT) comparing a new antihypertensive to placebo. The study reports a relative risk reduction (RRR) of 40%, but the absolute risk reduction (ARR) is only 2%. Which statement best interprets these findings?
- The ARR is more clinically meaningful because it reflects the actual magnitude of benefit in the population studied (Correct answer)
- The RRR is more clinically meaningful because it accounts for baseline risk differences
- Both values are equivalent measures of clinical significance
- The RRR should always be used when counselling patients about treatment benefit
Correct answer: The ARR is more clinically meaningful because it reflects the actual magnitude of benefit in the population studied
The ARR (2%) reflects the true absolute difference in event rates between groups, giving the number needed to treat (NNT = 50). RRR can appear impressive even when baseline risk is low, making ARR and NNT the preferred measures of clinical significance.
Question 2: Which type of drug information resource is considered a primary literature source?
- Compendium of Pharmaceuticals and Specialties (CPS)
- A peer-reviewed clinical trial published in NEJM (Correct answer)
- Lexi-Comp drug monograph
- A pharmacotherapy textbook chapter
Correct answer: A peer-reviewed clinical trial published in NEJM
Primary literature consists of original research published in peer-reviewed journals (e.g., clinical trials, case reports). The CPS and Lexi-Comp are tertiary sources; textbook chapters are also tertiary sources that synthesize existing data.
Question 3: In a clinical trial, a p-value of 0.03 is reported for the primary endpoint. Which interpretation is MOST accurate?
- There is a 3% chance the new drug is ineffective
- There is a 97% probability the treatment is clinically significant
- If the null hypothesis were true, there is a 3% probability of obtaining results at least this extreme by chance (Correct answer)
- The trial has a 3% margin of error
Correct answer: If the null hypothesis were true, there is a 3% probability of obtaining results at least this extreme by chance
A p-value represents the probability of observing results as extreme as those obtained (or more extreme) assuming the null hypothesis is true. It does not directly represent the probability of efficacy or the chance of error.
Question 4: A pharmacist needs to quickly verify whether two IV medications are physically compatible in the same bag. Which resource is MOST appropriate for this specific query?
- Pharmacotherapy: A Pathophysiologic Approach
- Trissel's Handbook on Injectable Drugs (Correct answer)
- The Compendium of Pharmaceuticals and Specialties (CPS)
- A published meta-analysis on IV drug safety
Correct answer: Trissel's Handbook on Injectable Drugs
Trissel's Handbook on Injectable Drugs (published by ASHP) is the primary reference for IV drug compatibility, stability, and admixture information. The CPS provides product monographs but not systematic compatibility data.
Question 5: Which study design provides the highest level of evidence when evaluating the efficacy of a pharmacological intervention?
- A well-designed cohort study with a large sample size
- A double-blind randomized controlled trial (RCT)
- A systematic review with meta-analysis of multiple RCTs (Correct answer)
- An expert consensus guideline based on clinical experience
Correct answer: A systematic review with meta-analysis of multiple RCTs
Systematic reviews with meta-analysis sit at the top of the evidence hierarchy because they pool data from multiple RCTs, increasing statistical power and reducing individual study bias. A single RCT ranks below this pooled analysis.
Question 6: A pharmacist reads a study that found a new statin reduced cardiovascular events with an NNT of 200 over 5 years. How should this value be interpreted?
- 200 patients must be treated for 5 years to prevent one cardiovascular event (Correct answer)
- The drug prevents cardiovascular events in 200% of patients over 5 years
- 1 in 200 patients will experience a serious adverse effect
- The drug is 200 times more effective than placebo
Correct answer: 200 patients must be treated for 5 years to prevent one cardiovascular event
NNT (Number Needed to Treat) is the number of patients who must receive the treatment over the specified period to prevent one additional outcome event. NNT = 1/ARR. An NNT of 200 means treating 200 patients for 5 years prevents one event.
PEBC Drug Information and Literature Evaluation
A pharmacist is evaluating a randomized controlled trial (RCT) comparing a new antihypertensive to placebo.
The study reports a relative risk reduction (RRR) of 40%, but the absolute risk reduction (ARR) is only 2%.
Which statement best interprets these findings?