"The AMA Masterfile misclassifies some specialist physicians, such as hospitalists and emergency department physicians, as general internists and family physicians," according to the Dartmouth report.
Sources for the AMA dispute some of Chang's findings, saying that the association relies on many databases for information. However, the AMA did not immediately respond for comment on the Dartmouth report.
As far as Chang is concerned, research and healthcare planning that relies on the AMA Masterfile "will not accurately measure the "primary care workforce."
"Many of the physicians who would be classified as providing primary care by the AMA Masterfile were either not providing care to fee for service Medicare beneficiaries or were providing nonambulatory or specialty care."
"Similarly," it adds, "a significant proportion of the physicians delivering primary care services as per Medicare were not classified as office-based primary care physicians in the AMA Masterfile."
In driving home its point in the study, the researchers decided then not to rely solely on the AMA Masterfile because of questions of its accuracy, Chang says. As part of their review, they also used clinical primary care FTEs derived from Medicare claims for beneficiaries as a "secondary measure of primary care physician workforce."
The researchers based their findings on a sample of more than 5 million Medicare beneficiaries in in 2007 in 6,542 primary care service areas and their hospitalization claims for 12 conditions that can be avoided when good care is provided within a clinic or office visit.
Chang says she believed it was important for her study to verify exactly where funds were allocated related to primary care services, particularly in outpatient settings.
"If they allocate and put the resources only to train primary care that may not be much help," she said.