Selecting a suitable appointment system in an outpatient setting.

One of the principal causes of waiting time in outpatient departments is the lack of well-designed appointment systems. A conceptual framework is given for dealing with existing appointment systems and to explain their working. The variables that play a role with respect to the appointment system are discussed. All different appointment systems can be compared according to their effect on the patients' waiting time and the physician's idle time, when the systems are expressed in terms of a new variable called "prepunctuality." Prepunctuality means the difference between the time of a patient's arrival at the clinic and the expected time of treatment, and is caused by the patient's own earliness, physician's lateness and the earliness induced by the appointment system chosen. The relationship between prepunctuality and both waiting and idle time was investigated by means of a computer simulation model. In this way, the consequences of using different appointment systems have been clarified, expressed in mean waiting time for the patient and total idle time for the physician. Given certain standards for waiting and idle time, the calculated results can be used to determine an appropriate appointment system and the corresponding waiting and idle time for the range of most common clinic situations. Examples are given to illustrate how these results can be used.