How is waiting time calculated?

'New Ways of Defining and Measuring Waiting Times' allows a truer measure of patients' waiting times to be calculated. This truer picture takes account of periods where the patient is unavailable for treatment (e.g. holidays) and also delays in treating a patient because of missed appointments and patient cancellations. The system takes account of patient responsibilities, in particular the acceptance of "reasonable" offers of appointment.

'New Ways' introduced two important new concepts in measuring waiting times:

1. Resetting the clock

If a patient accepts an offer of admission but does not attend their appointment, then they are recorded as a Did Not Attend (DNA) and their waiting time clock is reset to zero from the date of their appointment.

If a patient cancels an appointment (this is known as Could Not Attend (CNA)) then their waiting time clock is reset to zero from the date the appointment is cancelled.

If a patient turns down two "reasonable" offers of appointment dates then their waiting time clock is reset to zero from the date that the second offer was refused.

A reasonable offer must be at least 21 days in advance.

We call the latest date on which the waiting time clock is reset the effective start date.

2. Stopping the clock

Under new ways, if a patient is unable to attend an offered appointment due to social or medical reasons then they are recorded as unavailable, and their waiting times clock is stopped from the start date of this unavailability.

Periods of unavailability that are 7 days or less are generally not included in the calculation of waiting time.

Periods of unavailability of more than 7 days and which occur after the effective start date are known as effective unavailability as they have an effect on the waiting time calculation.

In the tables presented on ISD's waiting times web pages two types of waiting times are presented:

• Waiting times for patients who have attended for treatment (completed wait)
• Waiting times for patients who are still waiting (census wait)

The completed wait describes the time waited by patients who have been seen during a selected time period; the census wait is the time waited so far by patients still on a waiting list on a selected date.

The end of wait date (known as the reporting date) for the calculation of wait is then either the date the patient was treated (for patients who have been seen) or the census date (for patients still waiting).

More information is available about why analyses of both patients waiting and patients seen are published.

The calculation of waiting time is, then:

Reporting Date - Effective Start Date - Effective Unavailability