In the latest effort to expand its retail clinic business into specialized services, Walgreen Co. confirmed plans to launch a pilot program to treat the growing number of Americans with diabetes. Walgreens' Take Care clinics and CVS Caremark Corp.'s MinuteClinic subsidiary are this year rolling out specialized services that go beyond treating routine maladies. Diabetes is becoming one of the nation's top healthcare concerns and is regularly mentioned by President Barack Obama and members of Congress as a key area for improvement if medical costs are going to be kept under control.