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Representatives for all four insurers said their plans' H.I.V. drug coverage was in line with accepted medical practice and met requirements for coverage.
Karen Eldred, a spokeswoman for Cigna, noted that the company, like many other insurers, offers an array of plans in the federal marketplaces, including some that offer more comprehensive coverage.
A spokesman for Humana, Alex Kepnes, also noted that drugs for other diseases, like rheumatoid arthritis and multiple sclerosis, were also on a high payment tier.
Insurers have been asking consumers to pay more for the most expensive so-called specialty drugs, a trend that accelerated in the new marketplaces as insurers competed fiercely to keep premiums low. Patients with serious conditions, like cancer or rheumatoid arthritis, are finding that their pharmacy bills are skyrocketing.
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Advocates for people with other serious — and costly — medical conditions are likely to be watching this case closely, said Jennifer Kates, director of global health and H.I.V. policy at the Kaiser Family Foundation. If the federal office were to side with the patient advocates, "it would have broader implications because it would say this couldn't happen for those with diabetes, or any other kind of condition," she said.
The health care groups said what made this case different was that not every insurer placed such across-the-board restrictions on H.I.V. drugs.
"What is unique here is that it's every single drug, no matter whether it is generic or not," said Carl Schmid, deputy executive director of the AIDS Institute. "Other plans don't do this for H.I.V., and that's why we're proving that it's discrimination."
Other insurers offering silver plans in Florida's marketplace, including Florida Blue, Ambetter and Molina Healthcare, offered more generous coverage, with most out-of-pocket costs ranging from $10 to $25 a prescription, often after meeting a deductible, the groups said.
Mr. Schmid said many people with H.I.V. and AIDS welcomed the arrival of the new health care act because it meant they would have access to insurance after years of being shut out; before the law took effect, insurers could deny coverage to people with existing medical conditions like H.I.V. infection.
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But he said some patients were shocked when, newly covered, they were asked to pay pharmacy bills of up to $1,000 a month, in addition to the premiums they were paying. Some popular drugs, like Truvada, sell for $1,500 a month. Another therapy, Atripla, costs $2,400 a month, according to recent prices posted on the website of the National Institutes for Health.
Under the new health care law, out-of-pocket costs cannot exceed $6,350 a year, and some people with H.I.V. and AIDS can receive assistance for out-of-pocket costs through the federal Ryan White Program. But help is limited to those whose income falls below certain levels, which vary by state, and the federal funding must be appropriated each year by Congress.
Of the more than 1.1 million people living with H.I.V. or AIDS in the United States, about 400,000 are receiving treatment, and of those, about 23,000 are uninsured and eligible for coverage in the new marketplaces, according to a recent study by the Kaiser Family Foundation. Some in the exchanges may also have been previously covered through individual plans, and thousands more could begin receiving treatment now that they have insurance.
But although these patents' numbers are small, insurers have most likely taken note of the costs associated with treating H.I.V. patients: in a recent study of the first two months of prescription-drug use by people enrolled in new exchange plans, H.I.V. drugs accounted for 55 percent of all specialty drug claims, compared to 21 percent of claims made through employer plans during the same period.
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Mr. Turner said the groups took action partly to ensure that other plans did not follow in the footsteps of the insurers in the complaint.
"What we may be seeing is a race to the bottom," he said. "Plans don't want to be the preferred plan for people with H.I.V. and AIDS."