A new classification and measurement system of functional health
HAMG has developed the Classification and Measurement System of Functional
Health (CLAMES) to describe the impact of disease or injury in terms of functional
limitations. Like existing generic tools—the Health Utilities Index (HUI
3), the EuroQol five dimensions index (EQ-5D) and the SF-36 Health Status Questionnaire—CLAMES
measures health status and health-related quality of life. It can be used to
compare the impact of disease or injury in a population, to monitor population
health over time, and to identify disparities between socio-demographic groups.
CLAMES combines the attributes used in existing tools so that we can characterize
diseases and injuries across all aspects of health.
The challenge: covering the spectrum of health-related
functioning
Descriptions for health states relevant to Canadians
Contribution to program and policy decisions
In summary
Related reading
The challenge: covering the spectrum of health-related functioning
To cover the spectrum of health-related functioning—physical, mental
and social — we needed a classification system that included all significant
aspects of functional status resulting from diseases commonly experienced in
Canada.
We reviewed existing instruments, three of which (HUI 3, EQ-5D, and SF-36)
had been tested and validated in Canada. None of these could describe the complete
range of illness and injury, e.g., from the common cold to terminal cancer.
We thus selected, and modified as required, the most appropriate attributes
from these three instruments.
CLAMES uses eleven attributes, divided into core and supplementary attributes
(see Table 1). Core attributes describe the main domains of functioning affected
by common diseases and injuries. Supplementary attributes describe aspects
of functioning affected by a limited number of them.
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Table 1
Attributes used in CLAMES with sources from which they were adapted
|
| Core attributes |
|
Pain or Discomfort
|
HUI 3 |
| Physical Functioning |
SF-36 |
| Emotional State |
HUI 3 |
| Fatigue |
SF-36 |
| Memory and Thinking |
HUI 3 |
| Social Relationships |
SF-36 |
| Supplementary attributes |
| Anxiety |
EQ-5D+ |
| Speech |
HUI 3 |
| Hearing |
HUI 3 |
| Vision |
HUI 3 |
| Use of Hands and Fingers |
HUI 3 |
Our goal was to ensure that as far as possible, the six core attributes were
structurally and statistically independent (in other words, they each measure
a different aspect). They also needed to be validated and coherent (they measure
what they are intended to measure).
Each attribute has 4 or 5 levels, with level 1 representing no limitations
in functioning (see Table 2). Consistent with the definition of capacity used
in the International Classification of Functioning (ICF) developed by the WHO,
these attributes reflect what individuals are capable of doing and how they
could function given the opportunity. For instance, “social relationships” measures
a person’s intrinsic capacity for developing and maintaining social relationships,
regardless of opportunities or restrictions provided by his or her environment.
Table 2
Examples of levels for attributes used in CLAMES
|
| Fatigue |
1. |
Generally no feelings of tiredness, no lack of energy |
| 2. |
Sometimes feel tired, and have little energy |
| 3. |
Most of the time feel tired, and have little energy |
| 4. |
Always feel tired, and have no energy |
| |
|
| Social Relationships |
1. |
No limitations in the capacity to sustain social relationships |
| 2. |
Mild limitations in the capacity to sustain social relationships |
| 3. |
Moderate limitations in the capacity to sustain social relationships |
| 4. |
Severe limitations in the capacity to sustain social relationships |
| 5. |
No capacity or unable to relate to other people socially |
CLAMES has been refined subsequent to qualitative testing and peer review.
The review process concluded that CLAMES covers the main domains of functioning
with no apparent gaps.
Descriptions for health states relevant to Canadians
We have selected about 400 health states based on prevalence, mortality and
other indicators of policy relevance. A health state usually describes one
stage of a disease or its treatment. Description cards are identified with
random two-letter codes (see Figure 1, Sample health state description card,
which describes severe chronic asthma).
Figure 1: Sample health state description card
HEALTH STATE: ML
|
You have problems with the following: |
| Pain or Discomfort |
Moderate pain or discomfort |
| Physical Functioning |
Mild limitations in physical functioning |
| Emotional State |
|
Fatigue
|
Sometimes feel tired, and have little energy |
| Memory and Thinking |
|
| Social Relationships |
|
| Anxiety |
Mild levels of anxiety experienced occasionally |
Each description includes the six core attributes. To simplify the presentation,
we leave blank space to indicate that there are no limitations in an attribute.
Supplementary attributes are indicated as required (in the sample card, health
state ML includes anxiety).
Descriptions are based on the scientific literature and are reviewed for clinical
accuracy by a panel of medical experts. To date almost 300 health state descriptions
have been prepared.
Contribution to program and policy decisions
A subset of these standardized descriptions was used to elicit preference
scores from panels of Canadians.
The scores will be integrated with epidemiologic data in the Population Health
Impact of Disease, Injury and Health Determinants in Canada (PHI). The PHI
is developing estimates and tools that contribute to objective assessment of
the relative health impacts of various disease, injury and risk factors on
the Canadian population. The PHI will measure this impact in terms of morbidity
and mortality, combined into a single index or summary measure of population
health.
CLAMES could also be adapted for use on population surveys such as the Canadian
Community Health Survey to measure and monitor health status in terms of functional
limitations.
In summary
The Classification and Measurement System of Functional Health (CLAMES) is
a generic tool used to measure health status and health-related quality of
life.
This comprehensive tool permits comparable description and classification
of health states covering a broad range of severity levels and symptoms.
CLAMES was developed by HAMG to describe health states—generally, a
particular stage in the progression or treatment of a disease—in a standardized
and coherent framework.
In our next issue, we will discuss how we measured Canadian preferences associated
with these health states.
Related reading
Feeny D, Furlong W, Torrance GW, Goldsmith CH, Zhu Z, DePauw S, et al. Multiattribute
and single-attribute utility functions for the Health Utilities Index Mark
3 system. Med Care 2002;40(2):113-28.
Brooks R. EuroQol: the current state of play. Health Policy 1996; 37(1):53-72.
Ware JE Jr. SF-36 Health Survey manual and interpretation guide. Boston: The
Health Institute, New England Medical Centre; 1993.
Chatterji S, Üstün BL, Sadana R, Salomon JA, Mathers CD, Murray
CJL. The conceptual basis for measuring and reporting on health. Global Programme
on Evidence for Health Policy Discussion Paper No. 45. World Health Organization:
Geneva; 2002.
Sarah Gorber is a senior analyst in the Health Analysis and Measurement
Group. She came to HAMG in 2001, after working with the Applied Research
Branch at
Human Resources Development Canada. She has a master’s degree in Health
Education from Dalhousie University. Her current research interests include
health status and preference measurement and quality of life research. She
has played a major role in the development, testing and implementation of the
Measurement of Health State Preferences in Canada.
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