Waiting time is calculated differently between gastrointestinal endoscopy patients who have a Clinical urgency category of 4 Urgent, 5 Semi-urgent or 6 Non-urgent and those with a category of 9 Surveillance. 

Waiting time calculation
For category 4 Urgent, 5 Semi-urgent or 6 Non-urgent patients, waiting time is calculated as the total number of days from the Placed on list date to either the Removal date or the Census date, minus any days the patient was not ready for care, and also minus any days the patient waited with a less urgent Clinical urgency category than their category at the Removal date or at the Census date.
 
For category 9 Surveillance patients, waiting time is calculated as the total number of days from the Surveillance due date to either the Removal date or the Census date, minus any days the patient was not ready for care. 

Start and end dates 
For category 4 Urgent, 5 Semi-urgent or 6 Non-urgent patients:
The start of the waiting time is the Placed on list date. 
For GIE waiting list removals (Part A), the end of the waiting time is the Removal date. 
For GIE waiting list census (Part B), the end of the waiting time is Census date. 

For category 9 Surveillance patients:
The start of the waiting time is the Surveillance due date. 
For GIE waiting list removals (Part A), the end of the waiting time is the Removal date. 
For GIE waiting list census (Part B), the end of the waiting time is Census date. 
Where the patient was removed before the Surveillance due date, the waiting time should be recorded as 0 (zero). 

Not ready for care periods 
If there are any not ready for care (NRFC) periods, the total number of days a patient was not ready for care is made up of these NRFC periods. The NRFC period is the inclusive number of days from the NRFC start date to the NRFC end date. NRFC periods should not overlap however if this occurs the days are only counted once. 

Less urgent periods 
A patient's clinical urgency can be re-categorised over the course of their wait. If the patient had a period during the wait where their Clinical urgency category was less urgent than the category at the removal date or the census date, then this period should be subtracted from the total number of days waited. If a day has already been excluded due to an NRFC period, the day is excluded only once. 

When a patient is removed from a gastrointestinal endoscopy waiting list and requires reinstatement, the same service request should be reinstated where possible in order to continue the patient's waiting time from that previously accrued, with a not ready for care period applied where appropriate.