Those who have worked at the OAP, however, said the services are far more advanced than what is available at most companies. One former staff member, who asked not to be named, described the OAP as "the best health care on the planet."
Members of Congress interviewed for this story say they believe the model of ready primary care services offered by the OAP should be expanded nationwide, though few discussed the logistics of how those services could be offered.
Republican Rep. Lee Terry of Nebraska says he does not use the OAP and was unaware of the types of services it offers. "I don't participate," Terry said. "But I know there's an option that you could use them as your, in essence, family practitioner while you're here."
Terry is introducing a bill to expand another health care model used by Congress -- the Federal Employee Health Benefits Program -- to all Americans. The FEHBP is an insurance exchange that allows federal employees to choose health insurance from several options.
Asked if the model of primary care services provided by the OAP should also be included in his legislation, Terry said, "I think that's a fair question. ... [All Americans] should have that, because, frankly, having a physician you can call or contact actually helps drive down costs."
One aspect of the office's operations which remains unclear is just how the annual $503 fee is determined.
Until 1992, OAP services were free to members of Congress. But after former Sen. Harris Wofford of Pennsylvania angered members by introducing a bill to make Congress members pay market rate prices for using the OAP, a compromise was reached.
Instead of charging for each service, Wofford said, members of the House and Senate agreed to hire independent consultants to determine the average value of the services offered and to use that amount to determine an annual fee.
"We thought of the pricing much like an HMO," Wofford said of the compromise pricing model. "The attending physician at the time told me he had no interest in handling insurance or billing for each service available."
But Wofford said the House and Senate committees tasked with determining the fee each insisted on hiring their own consultants, leading to a split pricing system. According to press accounts from 1992, the Senate set the fee at $520; the House fee was set at $263 for the same care. At some point, sources say, the separate rates were scrapped and replaced with the single fee, now set at $503.
The Office of the Attending Physician refused to comment on the fee or why it has not changed significantly in 17 years, despite rampant inflation in all other areas of health care costs.
Anderson refused repeated requests for the Committee on House Administration to provide details of how the rate is determined or who determines it. "Members pay an annual fee determined by an independent actuary for use of the OAP services," Anderson responded each time he was asked about the pricing model.
While many former staff members told ABC News they believe the services of the Office of the Attending Physician were often abused by some members of Congress, others, including Balbona, said the office serves a necessary role protecting the legislative branch of the federal government. Balbona said he agreed to talk to ABC News to defend the O.A.P.
"They provide members an accessible, professional place to get services. The alternative would be members going throughout Washington, DC, interrupting their service to our country," Balbona said. "It's not a political perk. Much like a medic who's in combat, it's not a perk for those soldiers. It's part of the mission."