Waiting list statistics. III. Comparison of two measures of waiting times.

The length of time that patients spend on waiting lists is a topic of current concern. Calculating the proportion of patients who have been on a waiting list for a long time by taking a census of patients on the list at a single point in time will tend to yield a higher estimate than that obtained by calculating waiting times of patients admitted to hospital during a period of time. To illustrate this point the waiting times of patients in the Oxford region as measured by SBH 203 returns ("census" data) were compared with those as measured by the Hospital Activity Analysis ("event" data). As expected, the SBH 203 census returns showed a higher proportion of patients who had waited over a year compared with the "event" measure of all admissions. This difference, which is analagous to the difference between prevalence and incidence in epidemiology, should be considered when using data from these sources to calculate waiting times.