 OLDWICK, N.J.--BUSINESS WIRE--AM Best has commented that the Credit Ratings ratings of UnitedHealth Group Incorporated UnitedHealth Group Minnetonka, MN NYSE:UNH and its insurance subsidiaries remain unchanged following the announcement that the group will acquire Change Healthcare Inc. Change Healthcare Nashville, TN NASDAQ:CHNG, a leading health care technology company. The outlooks of the ratings remain positive. It is anticipated that Change Healthcare will be combined with 