Work Area / Health Economics / HE Evaluation / Measuring for HE Evaluation

Measuring and valuing outcomes

As noted above, different economic evaluation techniques use different methods to measure and value the consequences of health care interventions, reflecting different notions of efficiency. These are summarised in the Table below.

Measurement of Consequences in Economic Evaluation

Type of economic evaluation	Identification of consequences	Measurement & valuation of consequences
CEA CUA within the CEA umbrella	Single outcomes of interest, common to both alternatives, but achieved to different degrees Single or multiple outcomes, not necessarily common to both alternatives	Natural units (e.g. life-years gained, disability days saved, points of blood pressure reduction etc) Healthy years typically measured as quality-adjusted life-years (QALYs)
CCA	Single or multiple outcomes of interest, common to both alternatives, but achieved to different degrees	Natural units (e.g. life-years gained, disability days saved, points of blood pressure reduction etc)
CBA	Single or multiple outcomes, not necessarily common to both alternatives	Monetary units based on individual compensation

Guidance for measuring and valuing outcomes

To explore the methods available for measuring and valuing outcomes of public health interventions it may help to review existing methodological guidance. The National Institute for Health and Clinical Excellence (NICE) http://www.nice.org.uk/ reference case provides an example of formal guidance for the evaluation of health care interventions. It is recommended that all health effects on individuals are included, expressed in terms of quality-adjusted life years (QALYs) and without any adjustment for equity. The use of a standardised and validated generic instrument is recommended to quantify the effects of interventions in terms of health-related quality of life (HRQoL). To value people's HRQoL, expressed as utilities, it is recommended that the preferences of the general public are elicited using a choice-based method of valuation, such as the time-trade off or standard gamble technique as described next (Torrance, 1986).

National Institute for Clinical Excellence (2004) Guide to the methods of technology appraisal, April 2004. London: UK National Health Service, National Institute for Clinical Excellence.
http://www.nice.org.uk/

Torrance, GW. Measurement of health state utilities for economic appraisal - a review. Journal of Health Economics 1986; 5: 1-30.
http://ideas.repec.org/a/eee/jhecon/v5y1986i1p1-30.html

Standard Gamble (SG)
Using the SG technique to obtain utility values, respondents are presented with a choice between an intermediate, guaranteed health state and a gamble between full health and death. The probability of death (1 - P) is varied until a point of indifference is reached between the two choices. The value of P gives the utility value. The Figure below illustrates the SG technique.

The standard gamble technique

Time Trade Off (TTO)
Using the TTO technique, respondents state the length of time in full health that they consider to be equivalent to a longer period of time in poor health (health state i) as illustrated in the Figure below. The utility value for health state i is time x divided by time t.

The Time Trade Off technique

Besides the SG and TTO choice-based method of valuation, a non-choice based method is sometimes used such as a rating scale or visual analogue scale (VAS) as illustrated in the Figure below. Typically the VAS is on a 0 to 10 or 0 to 100 scale. The value is read off the scale.

The EQ-5D questionnaire

By placing a tick in one box in each group below, please indicate which statement best describes your own health state today.

Do not tick more than one box in each group

Mobility
	I have no problems in walking about
	I have some problems in walking about
	I am confined to bed
Self-Care
	I have no problems with self-care
	I have some problems washing or dressing myself
	I am unable to wash or dress myself
Usual Activities (e.g. work, study, housework, family or leisure activities)
	I have no problems with performing my usual activities
	I have some problems with performing my usual activities
	I am unable to perform my usual activities
Pain/Discomfort
	I have no pain or discomfort
	I have moderate pain or discomfort
	I have extreme pain or discomfort
Anxiety/Depression
	I am not anxious or depressed
	I am moderately anxious or depressed
	I am extremely anxious or depressed

QALYs combine changes in length of life and changes in health-related quality of life (HRQoL). Life expectancy is left in natural units. Values of HRQoL are valued on a 0 (death) to 1 (good health) scale. To calculate QALYs, the utility values are then multiplied by the time spent in the particular health state.

Utilities may be valued directly in studies, for example, alongside randomised controlled trials. Some repositories of HRQoL weights exist, as referenced below, which provide such weights for use when it is not be possible to gather original HRQoL weights (utilities) directly.

References for HRQoL estimates Tengs T, Wallace A. One thousand health related quality of life estimates. Medical Care. 2000; 38, 6, 583-637.
http://www.lww-medicalcare.com/pt/re/medcare/abstract.00005650-200006000-00004.htm;
jsessionid=FVpLxSymcngVJ1RQ9rz0zZc7Wpcjq2kJGMbGwZTyrZ8NBYQY685y!2089961419!-949856144!8091!-1

Currie, C., McEwan, P., Peters, J. et al. The routine collation of health outcomes data from hospital treated subjects in the Health Outcomes Data Repository (HODaR): Descriptive analysis from the first 20,000 subjects. Value in Health. 2005; 8, 581-590.
https://www.crc-limited.co.uk/portal/hodar.html

Reference for national HRQoL norms by age and sex Kind P, Hardman G, Macran S. UK population norms for EQ-5D. 1999. Centre for Health Economics Discussion Paper 172, University of York, York.
http://ideas.repec.org/p/chy/respap/dp172.html

References to estimate life expectancy
(http://www.gad.gov.uk/Life_Tables/Interim_life_tables.htm)