One of the most notable aspects of the Affordable Care Act was that insurance companies couldn’t discriminate against people with pre-existing conditions. But they have found ways to still do it, which could potentially throw off the whole system once patients start to congregate to different plans.

Companies might not be turning them away entirely now, but they are finding ways to essentially push people away with drug prescription pricing, according to a new study published in the New England Journal of Medicine.

Harvard researchers, Doug Jacobs and Benjamin D. Sommers, specifically looked at co-pays for the most commonly prescribed HIV medications – nucleoside reverse-transcriptase inhibitors, or NRTIs – within 48 mid-range cost insurance plans in 12 different states.

The Atlantic described the findings:

They found that in a quarter of the plans, insurers had listed the NRTIs in the highest co-pay tier, meaning that the customers would have to pay 30 percent of the cost or more. About half of these so-called “adverse tiering” plans also had a deductible specific to that drug. People enrolled in these plans would have to pay more than $3,000 more per year for their treatments, even if they used generics.

“If plans place all HIV drugs in the highest cost-sharing tier, enrollees with HIV will incur high costs regardless of which drugs they take,” the authors wrote. “This effect suggests that the goal of this approach—which we call ‘adverse tiering’—is not to influence enrollees’ drug utilization but rather to deter certain people from enrolling in the first place.”

Even with the benefits resulting from Obamacare requiring insurance enrollment to all people, there are clearly still issues with the system.

“The [Affordable Care Act] has already made major inroads in designing a more equitable healthcare system for people with chronic conditions,” Jacobs and Sommers concluded, “but the struggle is far from over.”