WASHINGTON — A review of a dozen Veterans Affairs medical facilities in North Carolina and Virginia identified widespread inaccuracies that vastly understated veteran wait times for appointments last year, leading the VA inspector general to conclude that VA scheduling data is still unreliable and a “high-risk” area for the agency.

The miscalculations, outlined in an inspector general report issued Thursday, masked actual demand for care and precluded veterans from getting private sector treatment, which they are supposed to be able to get if they have to wait longer than a month for a VA appointment.

The inspector general looked at primary and mental health care appointments for new patients and referrals for specialists and found that overall, 36% had to wait longer than a month for an appointment, but the VA scheduling system said only 10% had waited that long.

The report estimated that as many as 13,800 veterans should have been able to get VA-sponsored care in the private sector because of their long waits, but the VA never added them to lists authorizing them to receive outside care under the so-called Choice program.

VA staffers entered the wrong dates in the scheduling system in some cases and didn’t follow up on appointment requests in a timely way in others. In a few cases, medical center directors or other supervisory staff disagreed with national guidelines designed to ensure veterans see specialists within a time frame dictated by their referring doctor. So they just didn’t require staff to follow them.

The inspector general also reviewed records of veteran patients who were added to Choice lists and managed to get appointments outside the VA. Auditors found that 82% of them waited longer than 30 days, and on average, they waited nearly three months.

“Choice did not reduce wait times to receive necessary medical care for many veterans,” Larry Reinkemeyer, assistant inspector general for audits, wrote in the report.

The investigation is the largest on wait-time manipulation at the VA since 2014, when at least 40 veterans died waiting to be seen at the Phoenix VA while schedulers there kept secret wait lists hiding how long they were waiting. The inspector general has looked at more than 100 medical centers individually since then and found widespread problems, but the most recent investigation is the first to assess the reliability of wait-time data in an entire region, the mid-Atlantic in this case. And it identified flaws in the scheduling system still used by VA facilities nationwide.

VA Secretary David Shulkin, whom the Senate confirmed unanimously a few weeks ago, was undersecretary for health at the time of the audit, which stretched from April 2016 to last month. He said the agency has already taken action to improve wait times for the Choice program, and he disputed the findings about inaccurate wait times because he disagrees with the way the inspector general calculated them, according to his response included with the report.

“I cannot concur with some of the conclusions in this report nor use them for management decisions,” Shulkin wrote.

He said they are also based on outdated rules for scheduling appointments. Shulkin issued new rules in July.