About 20 years ago, I attended a lecture given by Andrew Stevens, a rather formidable and austere Professor of Public Health at the University of Birmingham.  He was setting out his epidemiologically based approach to health care needs assessment. He and his colleagues, James Raftery, Jonathan Mant, and Sue Simpson edited a series of books on the topic that sit on the shelf behind me1.  I refer to them on a regular basis.  They remain both grounding and inspirational reference material.

At the heart of his lecture and books series is a deceptively simple and timeless conceptual framework that I’ve relied on ever since, and most recently in our analysis of exploring GP practice consultation rates, the gap between need and supply of consultations, and GP practice productivity. 

Health service commissioning or planning had always felt like a messy, rudderless discipline to me.  There were problems, and there were numbers, but no coherent way to link them. This conceptual framework seemed to offer some purchase. 

The framework starts by defining three terms: need, demand, and supply, with respect to healthcare services.  These must be three of the most commonly used words in healthcare planning circles, but we tend to use them loosely. For this framework at least, tighter definitions are required. 

Here, ‘need’, means something quite particular, and can only be understood with respect to a specific service or intervention. A patient ‘needs’ service X or Y, if they have the potential to benefit from that service.  The presence or absence of that potential is a function of the patient’s characteristics and the evidence base.  

Demand is some request or outward expression of a desire for a service.  It may be logged within a service’s record system, but such a record is not essential for demand to exist.  It can come directly from the patient, or from someone acting on their behalf.  In some cases, such as screening, immunisation, or chronic disease management, the demand may originate from the service itself.

Supply is the easiest of the three terms to define. It is the delivery of a service or intervention to a patient.

Having staked out the territory, the framework offers two key insights. 

Insight 1: Need, demand, and supply, can be thought of as overlapping domains. 

They can coexist within a patient’s experience, but they can also be present independently and in pairs.  This is usually represented as a Venn diagram of three overlapping circles.  In the central area, where need, demand, and supply occur together, a patient needs (i.e. has the ability to benefit from) a specific service or intervention, that service is requested and received.  All good. 

But in all of the other domains, some loss occurs. It might be that resources are wasted, or that an opportunity to improve a patient’s health is missed. 

You can click on each of the segments in the diagram below to explore this further: