ICECAP-O

ICECAP-O in Economic Evaluation of Care for Older People

The ICECAP-O asks older people what they are able to do and be, rather than how healthy they are, and turns the answers into a single index for economic evaluation. Its developers describe it as the first use of the capabilities approach to build and value an instrument for the economic evaluation of health and social care, and its scale runs between no capability and full capability instead of between death and full health. That anchoring is the main thing a health economist has to keep in mind, because the zero point at no capability means ICECAP-O scores cannot be dropped into a QALY calculation in place of EQ-5D utilities. The instrument has mainly been included as a secondary measure in economic evaluations, often of services for older people where benefits such as independence or companionship can change while health-related quality of life stays flat.

Five capability attributes drawn from interviews with older people

The descriptive system came out of qualitative interviews with older people. Grewal and colleagues interviewed 40 people aged 65 and over with the stated aim of finding attributes for an index that focused on quality of life itself, not on health or other influences on quality of life. Further probing and analysis produced five conceptual attributes, and the authors observed that informants' quality of life was limited by the loss of the ability to pursue them, which is why the measure is framed around capabilities.

Coast and colleagues then refined the lay wording of the attributes and their levels through iterative qualitative work with 19 further informants in the UK. Each attribute has four levels. The developer's documentation codes the top level, full capability, as 4 and the bottom level, no capability, as 1, which is the reverse of the EQ-5D convention in which 1 is the best level.

With four levels on each of five attributes the descriptive system defines 4 × 4 × 4 × 4 × 4 = 1,024 capability states, each written as a five-digit profile such as 44444 for full capability on every attribute. The University of Bristol, which hosts the ICECAP measures, asks every user to complete a user agreement form before the measure is used.

UK index values estimated with best-worst scaling

Coast and colleagues used best-worst scaling to estimate general population values for every attribute level among people aged 65 and over, and the University of Bristol describes the resulting index values as coming from a best-worst scaling study of older people in England. In this form of best-worst scaling a respondent looks at a profile and picks its best and worst attribute level, and the pattern of choices gives relative values for all levels on a common scale.

The values were anchored so that full capability on all five attributes scores one and no capability on all five scores zero. The developer's guidance states that the value of a whole profile is found by adding the values of its five attribute levels, so the index is additive with no interaction terms.

$$S = \sum_{a=1}^{5} v_{a}(l_{a})$$

where $S$ is the ICECAP-O index score for one completed questionnaire, $a$ indexes the five attributes, $l_{a}$ is the level the respondent chose on attribute $a$ and $v_{a}(l_{a})$ is the published UK value for that level. The values themselves are distributed by the developers as scoring code and are not reproduced here, so any analysis should take them from that source rather than from a secondary paper.

This is a UK value set in the sense that it attaches population preference weights to every state of a descriptive system, but it differs from an EQ-5D value set in method and in anchors. The valuation used best-worst scaling rather than a time trade-off or standard gamble task, so the values carry no information about how many years of life respondents would give up to move between capability states.

What anchoring at no capability means for QALY arithmetic

A QALY weights each period of life by a utility on a scale where zero equals dead and one equals full health, so a gain of 0.1 sustained for a year is worth 0.1 QALYs. ICECAP-O zero is the state of no capability on all five attributes, and the best-worst scaling task did not ask respondents to trade length of life, so the index is not a utility scale anchored at dead. An ICECAP-O score of 0.7 is therefore not a health state utility value and cannot be added to or substituted for EQ-5D utilities in the denominator of a cost-utility analysis.

Analysts can still combine ICECAP-O scores with time. They can be combined, for example, as the area under the curve of index scores over follow-up, which gives a capability-weighted duration with the same structure as a QALY but a different unit.

$$C = \sum_{k=0}^{K-1} (t_{k+1}-t_{k}) \frac{S_{k} + S_{k+1}}{2}$$

where $C$ is the capability-weighted time for one person or arm, $t_{k}$ is the time in years of assessment $k$, $S_{k}$ is the ICECAP-O index score at that assessment and $K$ is the number of intervals between assessments. A difference in $C$ between arms can be set against a difference in cost, but the resulting ratio has no agreed threshold, a gap the review by Zhang and colleagues lists among the reasons ASCOT and ICECAP have had little influence on NICE decisions.

How ICECAP-O scores have been used in economic evaluation

Most economic evaluations that collect ICECAP-O place it beside a health measure. A systematic review by Proud, McLoughlin and Kinghorn of the instrument's first decade found good evidence of construct validity and responsiveness but some issues with content validity, and reported that in economic evaluations it had so far mainly been included as a secondary economic measure. One way to report such a study is a cost-utility analysis on EQ-5D QALYs as the primary result, with ICECAP-O change set beside costs in a secondary analysis or in a cost-consequence table.

NICE's guidelines manual, Developing NICE guidelines (PMG20), sets out its reference case in section 7.4 (table 7.1), with separate columns for different kinds of intervention. As the page stood in October 2026, the column for interventions with a social care focus lists capability or social care-related quality of life measures, such as ICECAP or ASCOT, as the measure of non-health effects when an intervention results in both health and capability or social care outcomes. Health effects are measured separately, so ICECAP-O results sit beside QALYs rather than replacing them.

Use in NICE guidance has been rare. Zhang and colleagues reviewed NICE social care and public health guidelines published before 26 August 2025 and found ICECAP as an outcome in 1% of eligible guidelines and the Adult Social Care Outcomes Toolkit in 4%, with neither measure significantly affecting committee decisions. The experts they interviewed pointed to underfunding, structural differences between social care and health, scarce training and resources, the lack of an established willingness-to-pay threshold and the existence of several versions with different value sets.

Illustrative worked example of a home reablement trial

All figures in this example are illustrative and do not come from a published trial. A trial randomises older people leaving hospital to a home reablement service or usual care and follows them for one year, measuring ICECAP-O and EQ-5D at baseline and at 12 months. The service adds GBP 600 per person to health and social care costs.

1. Capability-weighted time in each arm. Mean ICECAP-O scores are 0.70 at baseline and 0.78 at 12 months in the reablement arm, and 0.70 and 0.72 in the usual care arm. With one interval of one year, the reablement arm accrues 1 × (0.70 + 0.78) / 2 = 0.74 capability-weighted years and the usual care arm accrues 1 × (0.70 + 0.72) / 2 = 0.71.

2. Incremental capability gain. The difference is 0.74 minus 0.71, which is 0.03 years of full capability equivalent per person.

3. Cost per unit of capability gained.

$$\frac{600}{0.03} = 20000$$

where 600 is the incremental cost in GBP and 0.03 is the incremental capability-weighted time, giving GBP 20,000 per year of full capability equivalent.

4. Comparison with the QALY result. Suppose the same trial shows an EQ-5D gain of 0.01 QALYs. The cost per QALY is 600 / 0.01 = 60,000, or GBP 60,000 per QALY.

The two ratios answer different questions. On the QALY measure the service looks poor value against the thresholds NICE uses, while the ICECAP-O result records a gain that the EQ-5D barely detects. GBP 20,000 per year of full capability equivalent cannot be compared with any NICE threshold, because no threshold exists for that unit and the two scales have different zero points. A guideline committee would see both results side by side and judge whether the capability gain justifies the cost.

How ICECAP-O differs from neighbouring measures

The ICECAP-A is a later capability measure from the same group of researchers, developed for the adult population in general. It has its own five attributes and its own UK index values, so the two instruments should not be pooled or scored with each other's values. ICECAP-O is meant for people aged 65 and over, whose valuation sample it reflects.

ASCOT, the Adult Social Care Outcomes Toolkit, measures social care-related quality of life and is the instrument NICE names beside ICECAP for non-health effects. ICECAP-O asks about capability wellbeing whatever its cause, so a service can register on one measure and not the other.

The EQ-5D describes health and yields utilities anchored at dead and full health that feed QALYs. ICECAP-O describes capability wellbeing and is anchored at no capability, which is why analysts often collect both rather than choosing between them. Wellbeing in the subjective sense, such as life satisfaction or happiness, is a further construct again, because ICECAP-O records what a person is able to do rather than how the person feels about life. Social care is the setting in which the measure is most often used, not something it measures directly.

Common misreadings of ICECAP-O scores

Several errors recur when ICECAP-O results are reported or modelled. Most come from treating the index as if it were a health utility.

• Reading zero as dead. Zero is the profile with no capability on every attribute. The valuation did not trade length of life against capability, so ICECAP-O scores are not QALY weights.
• Applying a cost per QALY threshold. A cost per unit of capability gained has no agreed threshold, and comparing it with NICE's range in GBP per QALY mixes two different units, as the worked example shows.
• Summing the level codes. The codes 1 to 4 are labels for levels, and adding them gives a number with no preference weight. The index is the sum of the published values for each level.
• Assuming the measure covers health. Proud and colleagues found some issues with content validity, and the developers designed the measure around quality of life rather than health, so a health measure is normally collected alongside it.
• Mixing versions and value sets. Zhang and colleagues note that several versions of these measures exist with different value sets, so pooled or compared results need to state which instrument and which values were used.

Sources

• Coast J, Flynn TN, Natarajan L, Sproston K, Lewis J, Louviere JJ, Peters TJ. Valuing the ICECAP capability index for older people. Social Science and Medicine. 2008;67(5):874-882. doi:10.1016/j.socscimed.2008.05.015
• Grewal I, Lewis J, Flynn T, Brown J, Bond J, Coast J. Developing attributes for a generic quality of life measure for older people: preferences or capabilities? Social Science and Medicine. 2006;62(8):1891-1901. doi:10.1016/j.socscimed.2005.08.023
• National Institute for Health and Care Excellence. Developing NICE guidelines: the manual (PMG20), chapter 7, Incorporating economic evaluation, section 7.4 and table 7.1. First published 2014, page checked 17 October 2026. https://www.nice.org.uk/process/pmg20/chapter/incorporating-economic-evaluation
• Proud L, McLoughlin C, Kinghorn P. ICECAP-O, the current state of play: a systematic review of studies reporting the psychometric properties and use of the instrument over the decade since its publication. Quality of Life Research. 2019;28(6):1429-1439. doi:10.1007/s11136-019-02114-y
• University of Bristol. ICECAP-O (ICEpop CAPability measure for Older people) and ICECAP frequently asked questions. Pages checked 17 October 2026. https://www.bristol.ac.uk/population-health-sciences/projects/icecap/icecap-o/
• Zhang Z, Saygın Avşar T, Cooper S, Dietz J. Adult Social Care Outcomes Toolkit and ICEpop Capability Measure in decision making: a review of NICE social care and public health guidelines. Value in Health. 2026;29(1):108-118. doi:10.1016/j.jval.2025.08.021