A patient living with a chronic condition would trade 7 years in their current health state for 5 years in perfect health (and no more). Using the time trade-off method, what is their utility weight for this health state?
A0.71, calculated as 5/7
B0.40, calculated as (7 − 5)/5
C2.00, calculated as 7/5 − 1
DCannot be determined without knowing the patient's age
In the time trade-off method, utility = (years in perfect health the patient accepts) / (years in current health state). If the patient is indifferent between 7 years in their current state and 5 years in perfect health, their utility is 5/7 ≈ 0.71. Option B reverses the logic, and option C is nonsensical. Age is irrelevant to the TTO calculation — it captures preference strength at the point of indifference, not absolute time remaining.
Question 2 Multiple Choice
A new treatment costs $80,000 more than standard care and generates 1 QALY (2 years of life extension at utility 0.5). A second analyst reruns the calculation using EQ-5D tariffs instead of TTO weights and arrives at a utility of 0.3 for the same health state. What happens to the ICER?
AThe ICER remains $80,000/QALY because QALYs measure objective health improvement
BThe ICER rises to approximately $133,333/QALY because fewer QALYs are generated under the EQ-5D estimate
CThe ICER is unchanged because both methods measure the same underlying utility
DThe ICER falls because EQ-5D instruments are more precise than TTO
QALY = years × utility. Under TTO: 2 × 0.5 = 1 QALY → ICER = $80,000/QALY. Under EQ-5D: 2 × 0.3 = 0.6 QALYs → ICER = $80,000 / 0.6 ≈ $133,333/QALY. This is precisely why measurement method matters: different elicitation instruments assign different utility weights to the same health state, producing different ICER estimates — which can flip a coverage decision relative to a willingness-to-pay threshold.
Question 3 True / False
A treatment that generates QALYs entirely by improving quality of life (utility) is treated identically in cost-effectiveness analysis to one that generates the same number of QALYs by extending lifespan.
TTrue
FFalse
Answer: True
The QALY formula, years × utility, is agnostic about whether QALYs come from life extension or quality improvement. A treatment that adds 2 years at utility 0.5 (= 1 QALY) is treated identically to one that improves utility from 0.6 to 0.8 over 5 years (= 1 QALY increment). This equivalence is central to the QALY framework's power — and also a source of ethical controversy, since some argue that the route to health gain matters morally.
Question 4 True / False
The disability paradox refers to the finding that people with disabilities consistently report lower quality of life than healthy populations predict, confirming that QALY estimates from patient reports accurately capture the burden of their condition.
TTrue
FFalse
Answer: False
The disability paradox is the opposite finding: many people living with serious disabilities rate their quality of life as good or excellent — *higher* than healthy people imagining the same state would predict. This means population-based utility tariffs (derived from surveys of healthy respondents imagining disability) may *underestimate* the utility that adapted patients actually experience. Patient-reported utilities are often higher than tariff-based ones, complicating which source to use in ICER calculations.
Question 5 Short Answer
Why does the method used to elicit utility weights (TTO, standard gamble, or EQ-5D tariff) matter for health policy decisions, rather than simply reflecting measurement error that averages out?
Think about your answer, then reveal below.
Model answer: Each method captures a conceptually different quantity. TTO measures willingness to trade life-years; standard gamble measures tolerance of mortality risk; EQ-5D tariffs are derived from population surveys that may not reflect the preferences of people actually living with the condition. These are not interchangeable proxies for a single underlying utility — they can give systematically different values for the same health state. Because ICER = ΔCost / ΔQALY, even moderate differences in utility weight translate into large differences in ICER, potentially moving a treatment from cost-effective to unacceptable relative to a willingness-to-pay threshold.
The divergence between TTO and EQ-5D estimates introduces systematic, not random, error. A drug clearing a $50,000/QALY threshold using TTO weights might exceed $150,000/QALY using EQ-5D tariffs. Policymakers must be explicit about which method was used and what its limitations are — the choice is a substantive policy decision, not merely a statistical one.