Catchment areas in general practice and their relation to size and quality of practice and deprivation: a descriptive study in one London borough.

OBJECTIVE

To relate the sizes of general practice catchment areas in one London borough to list size, deprivation payments, medical staffing, and locally and nationally recognised measures of quality.

DESIGN

Study of general practice catchment area maps.

SETTING

London borough of Lambeth.

SUBJECTS

60 out of the 71 general practices in Lambeth.

MAIN OUTCOME MEASURES

Practice catchment area size with corrections for numbers of doctors and patients.

RESULTS

Catchment area size varied greatly between practices, showing an almost 150-fold difference between the largest and smallest practices. This size differential was even more marked when the size of the catchment area was corrected for the number of general practitioners in the practice, where a 300-fold difference was found. Substantial differences existed between practices in each of the four locally assigned quality bands. The weakest practices had catchment areas three times as large as those of the strongest practices. When corrected for medical staffing, the difference was eight times as great. A calculated measure of patient dispersion showed that the practice population of the strongest practices was four times as densely clustered as that of the weakest practices, whose patients were more widely geographically dispersed.

CONCLUSIONS

Large variations exist in the size of catchment areas of inner city practices even when corrected for numbers of doctors and patients. These differences are associated with variations in quality of care.