Pfizer Inc. signage is displayed on a monitor on the floor the New York Stock Exchange (NYSE) in New York, U.S., on Monday, June 20, 2016. U.S. stocks surged, with the S&P 500 Index jumping the most in four weeks, after the latest polls showed the U.K. campaign to remain in the European Union is gaining ground before Thursday’s referendum. Photographer: Michael Nagle/Bloomberg via Getty Images

High-profile advocacy groups for patients with cancer, Alzheimer’s, HIV and other diseases almost always accept funding from pharmaceutical firms, and many fail to report any contributions, new research shows.

At least 83 percent of the nation’s 104 largest patient advocacy groups take contributions from the drug, medical device and biotech industries, raising questions about whether they consistently put patients first, according to a paper published Wednesday in the New England Journal of Medicine.

“If you’re a policymaker and you want to hear from patients, there’s a danger if there’s an undisclosed or underdisclosed conflict of interest,” said Matthew McCoy, the paper’s primary author. “The ‘patient’ voice is speaking with a pharma accent.”

Of the 18 nonprofits not reporting pharmaceutical money, all but five failed to disclose their donors at all. Just one of the 104 nonprofits stated explicitly that it does not accept industry money.

Executives or former executives in the pharmaceutical industry serve on a third of the organizations’ boards, the researchers found.

These possible conflicts of interest are troubling, experts say, because while patients and drugmakers both want better treatments, they often have opposing goals.

Patients want cheaper medicine; the pharmaceutical industry wants to maximize revenue. Patients want information about the efficacy of certain drugs; the industry often seeks faster approvals for drugs, at which point the incentive to collect information about a drug has diminished, according to Vinay Prasad, assistant professor of medicine at the Oregon Health and Science University.

“Who is setting the narrative of what patients want?” he said.

Prasad is cited by the researchers but did not help conduct the study.

Research into the relationship between patient advocacy groups and the pharmaceutical industry is nascent, but the study finds that drug dollars prop up a higher proportion of patient groups than some previous papers.

A survey of patient advocacy executives published in the medical journal JAMA in January, for example, found that 67 percent of groups reported industry donors.

The latest study focused on larger groups that receive at least $7.5 million in revenue each year, which likely churned up more industry funding than a broader approach might have, said McCoy, a postdoctoral fellow in advance biomedical ethics at the University of Pennsylvania.

Also, pharmaceutical companies might funnel money to patient advocacy groups through other nonprofits, which would be harder to trace. “A patient organization may have gotten $1 million from the Making People’s Lives Better Fund. … That second degree of interrogation is not something we captured,” said McCoy.

About one-fifth of the patient advocacy groups studied accepted $1 million or more from drugmakers, but exactly how much those groups accepted is fuzzy. Half of the organizations disclosed their donations in ranges rather than precise amounts, and most of those reported their highest donations with an unbounded upper range, the study says.

Neither the NEJM paper nor the JAMA study in January examined how often a patient organization lobbied Congress, wrote letters to lawmakers or took stances on legislation.

But transparency in pharmaceutical ties is important even for advocacy groups with little presence on Capitol Hill, said Susannah Rose, one of the authors of the JAMA study.

Aside from steering legislation, the groups are important stakeholders in the delivery of care, research funding and patient assistance.

“Advocacy groups often give a voice to people who do not have a voice,” said Rose, scientific director of research in the Office of Patient Experience at the Cleveland Clinic and an expert in bioethics.

But whereas academic research centers, physicians and other medical professionals often feel pressure to reveal their associations with industry and face institutional checks against potential conflicts of interest, patient advocacy groups are too often overlooked, she said.

The paper comes at a time of both growing influence and heightened scrutiny of patient advocacy groups.

Pharmaceutical industry giant Pfizer said Friday it had received a subpoena related to its support of patient advocacy programs that offer financial assistance for Medicare patients’ copays. Johnson & Johnson disclosed Monday it had also received a subpoena from the U.S. Attorney’s Office for the District of Massachusetts seeking information about its support of organizations that pay for patient assistance. Those follow similar subpoenas sent to four drugmakers in 2015 and 2016 — Gilead Sciences, Jazz Pharmaceuticals, Valeant Pharmaceuticals and Biogen.

U.S. officials have not commented about the probe. But they could be trying to assess whether drugmakers are covering patients’ copays for expensive drugs and leaving taxpayers with the bill for the remainder of the cost, said Joel Hay, professor of pharmaceutical economics and policy at the University of Southern California. Hay has served as a paid expert witness in lawsuits against drugmakers. Pharmaceutical companies cannot subsidize the purchase of their products by Medicare.

Paying a relatively small subsidy for patients’ copays can also “take the pressure” off Congress to pass reforms that meaningfully slash drug prices in a way that undercuts the bottom line, said Prasad.

The Pharmaceutical Research and Manufacturers of America, the drug industry’s trade association, responded to questions about the NEJM study in a statement: “While we cannot speak for particular organizations, we have heard from many patients who are concerned about the growing out-of-pocket cost burden when trying to access needed health care services and treatments.”

This story was produced by Kaiser Health News, an editorially independent program of the Kaiser Family Foundation.