A majority of patients in the United States visited a doctor who received payments from drug companies, but most have no clue about it, according to a new Drexel University study.

About 65 percent of those surveyed as a part of the study by Genevieve Pham–Kanter, PhD, an assistant professor in Drexel’s Dornsife School of Public Health, visited a doctor within the last year who had received payments or gifts from pharmaceutical or medical device companies. What’s more: Only 5 percent of those surveyed knew that their doctor had received such payments.

“These findings tell us that if you thought that your doctor was not receiving any money from industry, you're most likely mistaken," Pham–Kanter said. "Patients should be aware of the incentives that their physicians face that may lead them to not always act in their patients’ best interest. And the more informed patients are about their providers and options for care, the better decisions they can make.”

Pham–Kanter’s study, published in the Journal of General Internal Medicine and done jointly with collaborators at Stanford and Harvard universities, was funded by the Greenwall Foundation. The study’s investigators conducted a nationally representative survey of more than 3,500 adults and linked their doctors to data from Open Payments, a government website that reports pharmaceutical and device industry payments to physicians.

Although two–thirds of all patients visited doctors who had received payments, those who visited certain types of specialists were even more likely to have seen a doctor who had been paid. For example, 85 percent of patients who visited an orthopedic surgeon saw a doctor who had received payments, and 77 percent of those who visited an obstetrician or gynecologist saw a doctor who had received payments.

“Drug companies have long known that even small gifts to physicians can be influential, and research validates the notion that they tend to induce feelings of reciprocity,” said co–author Michelle Mello of Stanford.

The amount received by physicians varied greatly, but the differences didn’t give the appearance of being random. In Open Payments, all physicians averaged $193 in payments and gifts. But when measuring only the doctors visited by participants in the survey, the median payment amount over the last year was $510, more than two–and–a–half times the U.S. average.

“We may be lulled into thinking this isn’t a big deal because the average payment amount across all doctors is low,” Pham–Kanter said. “But that obscures the fact that most people are seeing doctors who receive the largest payments.”

With so few people even knowing that information on their doctors and payments is available — just 12 percent in the study — it’s interesting to note the differences in who does seem to know about them.

In the three Sunshine states — where transparent doctor payment information has been available for some time — people were about half as likely to see physicians who’d received payments as patients in other states (34 percent to 66 percent). The authors surmised that even if patients don’t know about the information, physicians could be more likely to shy away from taking industry payments if they know the information is public.

“Transparency can act as a deterrent for doctors to refrain from behaviors that reflect badly on them and are also not good for their patients,” Pham–Kanter said.