HAC Cost-Effectiveness Analysis 2 — Questions and Answers
Question 1: In a cost-effectiveness analysis, the incremental cost-effectiveness ratio (ICER) is calculated as:
- Total cost of intervention divided by total QALYs gained
- Difference in costs divided by difference in health outcomes between two alternatives (Correct answer)
- Cost per patient treated divided by average survival benefit
- Net present value of intervention divided by number of patients
Correct answer: Difference in costs divided by difference in health outcomes between two alternatives
The ICER compares the additional cost of one intervention over another relative to the additional health benefit it provides.
Question 2: Which type of sensitivity analysis tests the impact of simultaneously varying multiple input parameters?
- One-way sensitivity analysis
- Deterministic sensitivity analysis
- Probabilistic sensitivity analysis (Correct answer)
- Threshold sensitivity analysis
Correct answer: Probabilistic sensitivity analysis
Probabilistic sensitivity analysis (PSA) assigns distributions to parameters and simultaneously varies them using Monte Carlo simulation.
Question 3: A healthcare intervention has an ICER of $45,000 per QALY. Using the US threshold of $50,000–$150,000 per QALY, this intervention is considered:
- Not cost-effective and should be rejected
- Cost-effective at the lower bound of the threshold (Correct answer)
- Dominant over the comparator
- Dominated by the comparator
Correct answer: Cost-effective at the lower bound of the threshold
An ICER of $45,000/QALY falls below $50,000, making it cost-effective even at the most conservative US threshold.
Question 4: What does a cost-effectiveness acceptability curve (CEAC) display?
- The probability that an intervention is cost-effective across a range of willingness-to-pay thresholds (Correct answer)
- The cumulative cost of treatment over the intervention period
- The sensitivity of the ICER to changes in discount rate
- The net monetary benefit at a fixed threshold
Correct answer: The probability that an intervention is cost-effective across a range of willingness-to-pay thresholds
A CEAC shows, for each WTP threshold, the probability that the intervention is cost-effective based on PSA results.
Question 5: In a Markov model used for CEA, 'cycle length' refers to:
- The total duration of the analysis horizon
- The time period after which patients can transition between health states (Correct answer)
- The number of Monte Carlo simulations run
- The discount period applied to future costs
Correct answer: The time period after which patients can transition between health states
Cycle length defines the intervals at which transitions between health states occur in a Markov model.
Question 6: Which perspective in CEA includes only direct medical costs paid by the insurance payer?
- Societal perspective
- Patient perspective
- Payer perspective (Correct answer)
- Provider perspective
Correct answer: Payer perspective
The payer perspective captures reimbursed medical costs but excludes patient out-of-pocket expenses, productivity losses, and indirect costs.
Question 7: Half-cycle correction in Markov models is applied to:
- Adjust for the probability of dying mid-cycle
- Correct the overestimation of time spent in each state when events occur throughout a cycle (Correct answer)
- Reduce the discount rate for long-term projections
- Balance transition probabilities to sum to one
Correct answer: Correct the overestimation of time spent in each state when events occur throughout a cycle
Half-cycle correction assumes events occur on average at the midpoint of each cycle rather than at the start, reducing systematic bias.
HAC Cost-Effectiveness Analysis 2
In a cost-effectiveness analysis, the incremental cost-effectiveness ratio (ICER) is calculated as: