Doctors are paid higher fees in the United States than in several other countries, and this is a major factor in the nation's higher overall cost of healthcare, says a new study by two Columbia University professors, one of whom is now a top health official in the Obama administration. ?American primary care and orthopedic physicians are paid more for each service than are their counterparts in Australia, Canada, France, Germany and the United Kingdom,? said the study, by Sherry A. Glied, an assistant secretary of health and human services, and Miriam J. Laugesen, an assistant professor of health policy at Columbia. The study, being published Thursday in the journal Health Affairs, found that the incomes of primary care doctors and orthopedic surgeons were substantially higher in the United States than in other countries. Moreover, it said, the difference results mainly from higher fees, not from higher costs of the doctors' medical practice, a larger number or volume of services or higher medical school tuition. Such higher fees are driving the higher spending on doctors' services, the study concluded.