Issues in valuing health outcomes in terms of QALYs

Group B:Norman Daniels, Mark Kamlet, Alistair McGuire, Erik Nord, George Torrance,

Milton Weinstein

The QALY

• Metric for measuring or estimating the value of health scenarios or outcomes.

• Equals the value of a healthy life year or an outcome equivalent to that.

Ambition

• To value all health outcomes on a common scale, whatever the type of health problem involved and whatever the effect on length of life.

• Aid decision making. Does not set aside the need for fair, democratic procedure.

The standard QALY procedure .. consists in:

(1) weighting life years according to their quality (healthwise) and proximity in time, (2) valuing a multi-year life scenario as the sum of the weighted life years in the scenario and (3) estimating the value of one scenario relative to another as the difference between the sums of weighted life years. Each of these steps raise methodological questions. The most salient ones, which we first address, are:

Most salient methodological questions

Re step 1 in the QALY procedure:

What are the most appropriate methods for weighting for quality of life?

Should there be additional weighting for severity?

Most salient methodological questions (ctd)

Re step 2 in the QALY procedure:

Is the value of a multi-year scenario simply the sum of the weighted years in the scenario?

HYEs question this. But also:

Is the value of two years really twice that of one year (even if the quantity is twice as large)?

Most salient methodological questions (ctd)

Re step 3 in the QALY procedure:

Is the value of a movement from one scenario to another simply the difference between the two scenarios valued independently?

Most important: The assumption implies that saving the life of people with chronic illness or disability carries less value than saving the life of otherwise healthy people.

But also:Does SG-disutility(A) = 2 x SG-disutility(B) necessarily imply

utility(A=>B) = ½ x utility(A=>Healthy)?(Could change of viewpoint/expectations mean that the second equation (viewpoint of the ill) does not necessarily follow from the first (viewpoint of the healthy)?)

Another important question

• The discount rate for distance in time

Less pressing questions

• Age weighting• Altruism

The answers to the methodological questions

depend on which questions QALYs are meant to address

Main purposes of QALYs

• Aid individual decision making

• Aid societal resource allocation

Questions in individual decision making:

• Which treatment should I choose?

• How should I prioritise in my insurance package?

Questions in societal resource allocation

• How much value does the average person assign personally to avoiding different types of health losses in the future (quality of life and life years)?

Use: Valuing health programs ex ante in terms of ’the sum of self interest’. • How much do people with different conditions actually suffer, and how much value do

they place ex post on different treatments?

Use: Judging ’value for money’ in ongoing activities/programs (’societal audit’).

• When thinking about both efficiency and fairness, how highly does the general public value programs for different categories of patients? (Note: The point is inclusion of fairness. PTO is not necessarily only about ’others’.)

Use: Valuing health programs ex ante in terms of population preferences for priority setting.

The various questions call for QALYs based on different concepts of value, different respondents and

different health state valuation techniques

Which treatment should I choose? Ex ante desirability, community members, SG/TTO/RS

How should I prioritize in my insurance package?

Same

Aggregate personal valuation of avoiding different health losses in the future.

Same

Evaluating ongoing activities: What is actual suffering and what are actual effects of treatments?

Experienced utility, patients/disabled people, SG/TTO/RS

How much do people value programs for different groups, given concerns for both efficiency and fairness?

Overall societal value, community sample, PTO

Dependency between valuations

Experienced utility Ex ante desirability

Overall societal value

(Judgments of ex ante desirability should be informed by experienced utility, and overall societal value judgements should be informed by both the former.)

• The two previous slides may serve as our first proposals for a consensus in Philadelphia.

• We may now address the methodological questions raised in slides 5-7 in more detail within the context of each of the three concepts of value: Ex ante desirability, experienced utility and overall societal value. We first focus on societal resource allocation (rather than individual decision making).

Methodological questions in societal resource allocation (slides 5-7):

Summary of what reflection and evidence suggests.

Value type: Question:

Aggregate personal ex ante

Experienced utility

Overall societal value

Appropriate health state valuation technique?

SG, TTO RS (due to insensitivity in SG and TTO)

PTO

Severity weights needed?

No No Covered by PTO

Value proportional to duration?

Probably not (fresh evidence)

Uncertain No

Value of life saving proportional to value of end state?

Clearly not Clearly not Clearly not

Value proportional to ’size’ of health gain?

Perhaps not(fresh evidence)

Perhaps not No

A closer look at weighting techniques

• SG, TTO, RS, PTO

Multi-attribute utility instruments

• Which are they?• Variation in values for the same states.• What to do about that.

A closer look at assumptions about the value of changes in health

Effect and value (1)• Societal decisions about resource allocation

1

A B0

• Daniels and Nord, Amsterdam 1992: If the arrows represent the maximum obtainable (potentials) in the two groups, then V(B)~V(A).

Effect and value (2)

• Gained years

• A 20

• B 10

• V(A) probably not = 2 x V(B), even disregarding discounting for distance in time. E.g. Dolan and Cookson, 1998.

Effect and value (3)

• Life saving

1

0A B

V(B) = V(A) both from societal and individual view point

Effect and value (4)

• Health improvements

1

0A B C D

If V(B) = V(A) also in individual utility (U), perhaps U(C) not much greater than U(D)

Effect and value (5)• Valuing improvements X and Y vs judging the disutility of conditions A

and B from the viewpoint of the healthy

QALYs: State A vs B Actual question of interest: V(X) vs V(Y)

• 1

B XY

A

• 0• In QALYs, the result from A vs B is used to value X vs Y. But the viewpoints are

different. So even if V(A)=0.6 and V(B)= 0.8 given healthy, V(X) may be less than 2 x V(Y) given state A.

Effect and value (6)

• Implications

• To say that the value of saving life should count as 1 ’regardless’ can lead to inconsistency:V(0 =>A) + V(A =>Healthy) > V(0 => Healthy)

But desire for mathematical consistency should not trump the need to model the real world correctly.

Effect and value (7)• Proposed solution in cost value analysis: Transform utilities. Difference between

vertical arrows < difference between horisontal arrows. Note: No inconsistency.

• Values for valuing change

• 1

• 0 1 Utilities from the viewpoint of healthy

A B

Effect and value (8):Useful to distinguish between

the following viewpoints

1. Ex ante to illness: Preferences for insurance2. Ex ante to treatment: Strength of desire for

treatment3. Ex post to treatment: Satisfaction/increase in

well being.

In (1), it is possible that feelings in (2) and (3) will be anticipated.

Other issues

• Discounting for distance in time• Age weighting• Altruism• Negative health states, maximal endurable

time

Individual decision making

• Shall we spend time on this?

Some tentative conclusions so far

• Experienced utilities are needed as inputs in all salient types of valuation.

Conclusions ctd

• In the model for aggregate ex ante self interest valuation (standard QALYs) of gains in health, the importance conventionally assigned to the disutility of health states and ’effect size’ needs to be reconsidered.

• Most importantly, the valuation of life saving needs to be separated from the valuation of health states.

Conclusions ctd

• Also, the problem of value variation across MAUs needs to be adressed.

Conclusions ctd• The three main types of societal economic evaluation

should have different names: Cost-utility ex post, cost-utility ex ante and cost value (concerns for fairness is not utility).

• All three types of evaluation can provide useful information for decision makers.

• Since the three types of evaluation may yield quite different results, any cost-per-QALY ’league table’ must be specific to one type of evaluation.

• Journals should require of papers that the type of evaluation be specified and that comparisons be made within types only.

Final remark

• Speculation: Based on similarities in values obtained in experienced utilities, some ex ante standard gambles and PTO suggest a structure of values with upper end compression that could serve as a rough guide in the field?