WASHINGTON — The Department of Veteran Affairs says it spent $2.3 billion on its electronic health record system from fiscal 2015 through 2017, but the Government Accountability Office said it found only $1 billion of the spending to be “sufficiently reliable.”

According to a new report by the Congress’ watchdog agency, the VA didn’t follow “a well-documented methodology” to determine what costs were actually related to the system, called VistA.

“VA’s total does not accurately reflect the development and sustainment costs for VistA,” the GAO report wrote. It warned that VA’s failure to keep track of its spending on VistA means “the department, legislators and the public do not have the comprehensive, reliable information needed to understand how much it actually cost to develop and maintain the system.”

The GAO concluded that records for $1.3 billion that the VA spent on VistA’s infrastructure, its related software and personnel were either not accurate, not well-documented, not credible or not comprehensive. It also pointed out that VA omitted VistA-related costs on additional hosting, and data standardization and testing from the total.

The 36-year-old VistA — formally known as the Veterans Health Information Systems and Technology Architecture — contains electronic health records for patients, support clinics and medical centers, and also has other functions such as library and billing systems. The VA relies on it to provide health care services to approximately 9 million veterans and their families.

Carol Harris, director of information technology acquisition management at GAO, said in a Thursday hearing that VA’s actual spending on VistA “is likely to be more than the $2.3 billion.”

For example, the VA told GAO investigators last June that the cost on additional hosting was about $238 million per year. But shortly after that, the agency said the cost was actually $950 million. In the end, VA reported zero dollars for additional hosting.

Harris said the VA’s subject matter expert agreed that $950 million was “off-base.” But “the fact that the additional hosting line item was not included in the $2.3 billion estimate suggests that the number is higher,” she said.

When asked by lawmakers on Thursday about why the VA failed to implement the cost-tracking methodology — called the Technology Business Management framework — Paul Tibbits, executive director of technical integration in the VA’s Information and Technology Office, said, “this methodology is relatively new. … Some of the methodology we have used, for example on the personnel cost, we’ve not up to now seen the need to classify personnel cost by system.”

“We will be, in the future, consistent with the TBM framework,” Harris added.

VA’s loose cost-tracking record on VistA also casts doubt on its 10-year, $10 billion migration to the commercial electronic health record system Cerner and its estimate on the cost.

Tibbits told lawmakers that the VA estimates the minimum cost to sustain VistA over the transition period is $4.98 billion, which takes up almost half of its $10 billion budget cap for the whole process announced in May 2018.

“Until the new electronic health record solution is implemented across the VA enterprise, VistA remains VA’s authoritative source of veteran data,” he said. “Sustaining VistA for the duration of the electronic health record modernization ensures that VA continues to provide uninterrupted care and services.”

In his testimony, Tibbits also said that VA officials are developing a methodology to reliably identify and report the total costs of VistA sustainment.