4. Rheumatoid Arthritis (RA): RA is a symmetrical distal inflammatory poly arthritis condition. The criteria developed and validated by the American College of Rheumatology (ACR) has been used in numerous drug studies which requires at least four of these seven criteria for diagnosis (morning stiffness, arthritis of three or more joint areas, arthritis of the hands, symmetric arthritis, rheumatoid nodules and classic radiographic erosive changes). Immunologic studies include positive rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibody.