New figures have shown that NHS Grampian is one of the worst-performing health boards in the country in meeting government waiting list targets.
An investigation by Audit Scotland found the north-east authority was second only to NHS Lothian in failing to treat patients referred to hospital within a 12-week period.
It also emerged the use of “unavailability codes” had fallen across the country since NHS Lothian was found to be manipulating figures to reduce waiting lists in 2011.
The report said most health boards were now treating patients within 18 weeks of referral, but the 12-week guarantee was described as challenging.
Only three boards have met the target each month since it was introduced in October last year.
The highest percentages of patients waiting more than 12 weeks in the month ending September this year were in Grampian (3.9%, 88 people) and Lothian (8%, 354 people).
Auditors also found Grampian had the second-highest percentage of patients “non-medically available” for reasons of patient choice at 60% after NHS Greater Glasgow and Clyde, both at 68%.
NHS Grampian also had the highest use of the code for patients wishing to be seen in their own health board area – 39% compared to a Scottish average of 16%.
Audit Scotland said the health board had identified a lack of capacity within its own area and had reported that many patients were not willing to travel to the Golden Jubilee Hospital in Clydebank or the Scottish Regional Treatment Centre at Stracathro, Angus.
“The board has invested in additional theatres, which will be operational in Woodend Hospital and Aberdeen Royal Infirmary from early 2014, and is in the process of recruiting additional consultants,” the report said.
An NHS Grampian spokeswoman said the health board is “committed” to meeting the waiting time targets.
She said: “We have invested in new theatres at ARI and Woodend. These are expected to be operational in the early part of 2014 and will significantly improve our capacity to treat patients within the target.
“If we cannot treat a patient within the guarantee time, we will offer them treatment elsewhere.
“However, patients in the north-east have long shown a preference to be treated locally and we respect their choice. The large number of people working in the energy industry – where shifts and work arrangements can change at short notice – also has an impact.”
NHS Highland was the only board in Scotland that has not provided a breakdown of patient-advised codes for inpatients since April 2013.
The report said that was due to “limitations” in the board’s electronic system, which is due for an upgrade in March 2014.
Auditor General for Scotland, Caroline Gardner, said: “It is encouraging to see the introduction of new patient unavailability codes that should help NHS boards identify problems with capacity and pressures in the system.”