Humana (HUM) is seeking to overturn an administrative appeal denial by the Centers for Medicare and Medicaid Services this week, upholding an October ratings downgrade that could potentially cost the health insurer billions of dollars in revenue.

A CMS administrative panel on Tuesday turned down Humana's bid to reverse the agency's ratings cuts of several Humana Medicare Advantage plans, the company disclosed in a court filing. It filed lawsuit in

a federal court in Texas soon after CMS trimmed its star ratings for the Medicare Advantage plans citing dropped calls and other problems for customers trying to reach Humana's call centers.

Reduced quality ratings have the effect of shifting many of Medicare customer to less lucrative plans. CMS also provides quality bonuses to plans with higher ratings, with the amounts reaching "hundreds of millions or even billions of dollars annually," the company said in its original complaint.

Humana has one more chance to convince the agency for reversal by April 28 before it can become official, according to the filing. If denied again, Humana expects to continue its legal fight before US District Court Judge Reed O'Connor in Texas.

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