Patient movements and the accuracy of the age--sex register.

This longitudinal study assessed the effects of patient movements on the accuracy of the age-sex register. For one year all patient movements into and out of five teaching practices were monitored and the ways in which inflation and deflation of the register can occur were identified and measured. Inflation has a greater influence than deflation on the accuracy of the register because:1. Practices can readily identify all new patients as they register and can include them in the age-sex register, but only a minority of patients (23.5 per cent) can be identified when they move away.2. The time interval between leaving a practice and registering with a new one is much shorter than that between leaving a practice and the practice becoming aware of the fact.Recommendations are made about how to make the register as accurate as possible.