Do referral rates vary widely between practices and does supply of services affect demand? A study in Milton Keynes and the Oxford region.

Two commonly held beliefs about referral rates were investigated in this study: first that demand for services is determined by supply and secondly that there is wide variation between general practices in their referral rates. All referrals to specialist outpatient clinics were recorded during two 11-week periods by general practitioners in eight practices in the new town of Milton Keynes and in 17 practices elsewhere in the Oxford region. During the first period, only a limited outpatient service was available in the new town; for many specialist services, people had to be referred to hospitals outside the district. Referral rates from Milton Keynes were very similar to those from the rest of the region. By the second period the range of specialist facilities available locally had expanded considerably with the opening of the new district general hospital and during this period there was a statistically significant but rather small increase in referral rates from Milton Keynes. Variation in referral rates between general practices within each geographical group was greater than that between the two groups. Overall, there was about a three-fold variation between general practices in outpatient referral rates which is considerably less than that commonly thought to exist.