Health Care Evaluation: Measures of supply and demand
Please see ‘The uses of epidemiology and other methods in defining health service needs and in policy development’ section for definitions of supply, demand and need.
Measures of supply and demand are important in local performance management and capacity planning of healthcare providers and also as part of national targets.
Measures of supply indicate the amount of care that can be made available and include:
- Staffing: consultants, total doctors, total nurses, managers and can be considered in terms of whole time equivalents and skill mix
- Beds available: available bed-days = no. of beds x no. of days in period (it is important to just count staffed beds not total beds)
- Equipment: eg MRI scanners, operating theatres
- Budget: surplus, debt, funds available for investment, other sources of income
- Ability to manage waiting times*
These measures can be used in isolation or combination, examples of combination measures include:
- WTE nurses / beds available
- consultants / operating theatre
- total doctors / beds available
- funds available per bed
Measures of demand indicate the quantity of health services the population wants. This may be legitimate need as well as desired demand (see definitions of demand and need), and so measures of demand must be interpreted with caution, for example:
- Inpatient admissions: a high number of admissions can reflect a high demand for a service, however admissions are also linked to the health status of a community or casemix - admissions are likely to be high in an elderly deprived population. Thresholds of admission by hospital or community staff also affect the number of people admitted though this is not a true measure of demand (it is actually a reflection of willingness to supply)
- Hospital catchment population: the number of people who fall within the catchment area of a healthcare provider. This will be affected by a number of factors such as: distance from the service user to the healthcare provider, ease of access, ambulance transfer time, range of services provided at each institution, quality and standards of care. Sometimes populations fall geographically between 2 providers and therefore estimates must be made to assess the proportion of a population who will attend a healthcare provider.
- Average length of stay (ALOS): may be a reflection of complexity of case mix (demand) or indeed poor discharge planning (supply)
- Waiting times*
These measures can also be used in isolation or combination, examples of combination measures include:
- Admissions per 1000 catchment population
- Hospital bed days demanded (= number of admissions during period x ALOS)
*waiting times can be considered as indicators of both supply and demand. Increasing waiting times could suggest both a decreasing supply in the face of constant demand or a rising demand in the face of constant supply. They must therefore be interpreted in context.
Healthcare organisations are monitored locally and nationally in terms of supply and demand of services. Indicators of supply and demand form part of the Healthcare Commission’s annual health check, for example in 2007/08, the following indicators (amongst others) were included :
- Maintain a maximum wait of 26 weeks for inpatients
- Maintain a maximum wait of 13 weeks for an outpatient appointment
- Maintain a maximum waiting time of two months from urgent referral to treatment for all cancers
- Maintain a two week maximum wait for rapid access chest pain clinics
- Maintain a two week maximum wait from urgent GP referral to first outpatient appointment for all urgent suspected cancer referrals
- Maintain the four hour maximum wait in A&E from arrival to admission, transfer or discharge
- Deliver a ten percentage point increase per year in the proportion of people suffering from a heart attack who receive thrombolysis within 60 minutes of calling for professional help
Further indicators used locally to monitor efficiency and performance within Trusts (with a view to meeting national targets) include:
- Throughput (patients per bed in a given period of time)
- Average length of stay in the over 65s age group compared to the under 65s age group
- New to follow-up appointments ratio in outpatient services
- % occupancy (= bed days demanded / bed days available x 100)
For all indicators, analysis can be undertaken by patient group, health resource group (HRG)*, by specialty, emergency versus elective care group, inpatient versus day case.
- * Healthcare Resource Groups (HRGs) are standard groupings of clinically similar treatments which use common levels of healthcare resource, for example, management of fractured neck of femur which can be emergency or elective. HRGs can be considered as a consistent “unit of currency” which enable the comparison of activity within and between different organisations and provide an opportunity to benchmark treatments and services to support trend analysis over time. HRGs are analogous to diagnosis related groups (DRGs) used in other countries like Australia, the United States, Belgium, Denmark, Finland, France, Greece, Iceland, Ireland, Italy, the Netherlands, Portugal, Spain and Sweden. The use of HRGs can enhance data collection, and support the fair distribution of resources to providers.
-  www.2008ratings.healthcarecommission.org.uk
-  Rogers et al, HRG drift and payment by results, BMJ 2005; 330 (7491):563
-  Dixon J. Payment by results—new financial flows in the NHS BMJ 2004;328:969-70
© Rosalind Blackwood 2009