Commentary: The basis of a more rational method of funding primary medical care?

Many previous studies investigating the association between socioeconomic factors and consultation rates in general practice have suffered from three limitations.

Firstly, many studies used socioeconomic data for areas rather than for individuals and the associations found in these studies may not hold at the individual level (the ecological fallacy).

Secondly, most previous studies have not taken into account the extent to which the provision of health services can generate demand for these services (supplier induced demand).

Thirdly, deprivation indices rather than separate socioeconomic variables have usually been used in the analyses.

In an innovative study investigating the association between socioeconomic factors and consultation rates in general practice, Roy Carr-Hill and colleagues used data from the fourth national survey of morbidity in general practice and ward census data in a multilevel statistical model. They then used this statistical model to try to disentangle the effect on consultation rates of the socioeconomic characteristics of individual patients (patient factors), the socioeconomic characteristics of the wards in which these patients lived (area factors), and the characteristics of the general practices with which these patients were registered (supply factors). Although many of their findings were probably to be expected, some important new findings did emerge from their study. For example, they showed that the socioeconomic characteristics of patients are a powerful predictor of consultation rates in general practice and that once individual characteristics are controlled for, area characteristics have little additional effect on consultation rates. Their other important finding was that the effect of socioeconomic factors on consultation rates varied between areas, implying that there should be some local discretion when resources such as deprivation payments to practices are allocated.

What are the implications of these results for the NHS? The main benefit of the work is that it is a major step towards the development of a more rational method of funding primary medical care services. These services have traditionally been funded on the basis of previous spending both at health commission level and general practice level, and this has led to inequities in funding.1 2 As a result of this study, the socioeconomic determinants of consultation rates in general practice are now much clearer. Although the development of a formula to allocate resources to health commissions for primary medical care services was not a primary aim of their study, the findings will help inform the debate on how such a formula should be developed. Carr-Hill et al suggest that their findings could also be used to develop a formula to help health commissions allocate resources to general practices, but such a formula would be difficult to implement.

Firstly, the populations served by general practices (typically 2000-20000 people) are much smaller than those of health commissions (typically around 500000 people). Consequently, small differences in the distribution of patients with a high demand for care can have a dramatic effect on the workload of general practitioners.

Secondly, the only socioeconomic variables routinely available for general practices are proxy variables derived by linking patients' postcodes with census data,3 and we do not know if these derived variables are accurate enough to be used to help allocate resources to general practices.4

Thirdly, the data in the morbidity survey have limitations (for example, the practices that participated were not a random sample), and these limitations need to be borne in mind when trying to generalise the findings to other general practices.5 Hence, although this study may help to pave the way towards a more rational method of funding primary medical care services at health commission level, more work still needs to be done to develop fairer methods of funding primary care services at general practice level.