In 1948, WHO defined health as “a state of complete physical, mental and social well-being, and not merely the absence of disease”. Health can be considered in terms of a person’s body structure and function and the presence or absence of disease or signs (health status); their symptoms and what they can and cannot do i.e. the extent to which the condition affects the person’s normal life (quality of life).
Health care is the prevention, treatment, and management of illness and the preservation of health through the services offered by health care organisations and professionals. It includes all the goods and services designed to promote health, including “preventive, curative and palliative interventions, whether directed to individuals or to populations”.
A) Measures of health status
Health status can be measured using pathological and clinical measures and is usually observed by clinicians or measured using instruments.
Types of disease measurement include:
- Signs - blood pressure, temperature, X-ray, tumour size
- Symptoms - disease specific checklists
- Co-morbidity - Charlson Index, ICED- index of co-existing disease (looks at both disease severity and functional severity), adverse events – pain, bleeding, readmission, complications (e.g. using Clavien-Dindo Classification of Surgical Complications).
It is always best to use an existing measure which has been tried and tested rather than inventing a new one. Use an existing standardised measure with proven reliability, validity and responsiveness. Criteria which should be applied when evaluating measures include:
- Acceptability - there should be a range across a measure with no floor or ceiling bias
- Reliability - test re-test (testing and retesting would give the same score), inter-rater (2 people assessing someone separately would give the same score- measured by the Kappa statistic*), internal consistency (Cronbach’s alpha - when series of questions are used to measure something e.g. the Oxford Hip Score, scores for the answers are often on a scale and added up to give a single total numerical value. Scales must have internal consistency i.e. the items should all measure the same thing. Cronbach’s alpha is a coefficient for assessing internal consistency of a scale. )
- Validity – sensitivity (identify those with disease correctly) and specificity (identify those without the disease correctly)
- Responsiveness - the degree to which a measure can detect change which is clinically meaningful.
*The kappa statistic measures inter-rate reliability. Kappa = (% observed agreement between observers – % agreement expected by chance alone) / (100% - % agreement expected by chance alone).
If the measure is intended for routine use as part of clinical practice:
- The measure should be appropriate/relevant
- The measure should be brief and simple to administer
- Feasible for routine use.
If it is not possible to use an existing measure, the next best thing is to adapt an existing measure, however it must be re-evaluated for reliability, validity and responsiveness in the new circumstances. Otherwise, a new measure needs to be developed and evaluated for reliability, validity and responsiveness.
Factors that can improve a test’s reliability include:
- Training of observers
- Clear definitions of terminology, criteria and protocols
- Regular observation and review of techniques
- Identifying causes of discrepancies and acting on them.
Methods that can increase validity include:
- Structured and standardised procedures for collecting clinical information
- Standardised protocols for scoring and interpreting
- Use of well-constructed instruments (i.e. with documented reliability and validity)
- Obtain appropriate reports of information.
Relationship between validity and reliability
What may be valid for a group or a population may not be so for an individual in a clinical setting. When the reliability or repeatability of the test is poor, the validity of the test for a given individual may also be poor.
B) Measures of quality of life
Quality of life is a measure of the difference between the hopes and expectations of the individual and the individual’s present experience.  Health-related quality of life is primarily concerned with those factors which fall within the spheres of influence of health care providers and health care systems.
- Health related quality of life can be measured by asking the patient directly or through various instruments.
- Measures of health-related quality of life can be applicable across different types of diseases, medical treatments and demographic / cultural groups or they may relate only to specific diseases, interventions or population groups. Population or disease-specific, whilst being very relevant to the population or people with the disease in question, make comparisons with the general population (who do not have the health problem) difficult. If such a comparison is important, a generic tool may be more useful. Generic and specific tools can be used in conjunction with each other.
- HRQoL measures are useful because they can establish the range of problems that affect patients, can pick up any on-going problems that might otherwise be missed, and can be a predictor of treatment success.
- HRQoL measures can be combined with measures of time in a particular health state, to form Quality Adjusted Life Years (QALYs) - see health economics section for more details.
Generic tools for measuring HRQoL include:
- Short form (SF)-36
- EuroQoL (EQ5D)
- Nottingham health profile (NHP)
- Sickness Impact Profile (SIP)
The SF-36 tool is a widely used tool which consists of a 36 item, self-administered questionnaire. It generates a score on 8 health dimensions plus 2 summary scores and is currently accepted as a gold standard measure. It is available in several languages and has been disseminated and adopted world-wide.
Disease specific tools include:
- Asthma Quality of Life Questionnaire - this consists of 32 items that produce four-dimension scores relating to activity limitations, symptoms, emotional function, and environmental exposure
- Mandatory PROMS from April 2009 - PROMS measures for hip and knee replacement and varicose veins (See 'Appropriateness and adequacy of services and their acceptability to consumers and providers' and http://content.digital.nhs.uk/proms)
- Mental health measures, such as the Warwick Edinburgh score (https://warwick.ac.uk/fac/med/research/platform/wemwbs/)
Population specific tools include:
- The Child Health and Illness Profile/CHIP - population-specific instruments are designed to be appropriate to particular demographic groups, such as children or elderly people. CHIP includes the five domains of satisfaction, comfort, resilience, risk avoidance, and achievement.
C) Measures of health care
Health care performance measures have already been described in 'Measures of supply and demand' and 'Study design for assessing effectiveness, efficiency and acceptability of services including measures of structure, process, service quality, and outcome of health care' in some detail. They may include:
- Patient satisfaction and experience and patient reported outcome measures. There are many tried and tested patient surveys in existence to capture satisfaction and experience as used by the Care Quality Commission and Picker Institute in national performance monitoring.
- Quality of health care can also be measured in terms of process as well as outcomes such as the implementation of guidelines, latest evidence and criteria for treatment and referral. In addition quality can be assessed by external organisations such as the Care Quality Commission through their monitoring and inspection processes and Monitor.
- Quantity or productivity of health care organisations (throughput of patients, bed occupancy and waiting times) are commonly used measures.
- Financial performance is now considered a key aspect of health care performance.
-  World Health Organisation Report. (2000). "Why do health systems matter?". WHO.
-  JM Bland, DG Altman, Statistics notes: Cronbach's alpha, BMJ 1997;314(7080):572 (22 February),
-  Fayers PM, Machin D. Quality of life: assessment, analysis and interpretation. Chichester: Wiley, 2000.
© Rosalind Blackwood 2009, Claire Currie 2016