Background In 2004, primary care payments for basic services and enhanced services were separated. This change has greatly facilitated the evaluation of the breadth and volume of services. Aim To determine whether larger practices produce a higher volume and greater diversity of enhanced services. Design of study Cross-sectional observational study using practice data obtained under the Freedom of Information Act 2000. Setting A total of 384 practices in 14 English primary care trusts. Method Practice data for all practices were collated for enhanced services, practice size, and deprivation. Diversity and volume of enhanced services were used as dependent variables in a series of multiple regression models to ascertain the effect of practice size, and any relationship with deprivation. Results Larger practices provided a greater diversity of services (P = 0.002), although this effect was not present in practices with more than 6330 patients. Practice size seems to influence the volume of enhanced services in general medical services, but this effect disappeared when deprivation was taken into account. Deprivation had a negative influence on the volume of enhanced services provided (P = 0.019). The effect of deprivation on volume persisted in practices with more than 6330 patients. Conclusion Current average-sized practices provide similar volume and diversity of enhanced services as those in the largest quartile; therefore, there seems to be little merit in creating 'supersurgeries' if the aim is to transfer work from secondary to primary care. There does not seem to be an upper threshold above which practice size creates spare capacity and expertise to deliver a significantly greater volume or more diversity of extra services.
