Diagnosis and differential diagnosis of rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a symmetric, peripheral polyarthritis of unknown etiology that, untreated or if unresponsive to therapy, typically leads to deformity and destruction of joints through the erosion of cartilage and bone. This topic will review the diagnosis, diagnostic criteria, and differential diagnosis of this disorder. The clinical features of RA are discussed separately. (See "Clinical features of rheumatoid arthritis".)

DIAGNOSIS

There is no single clinical, radiologic, or serologic test that enables a diagnosis of RA to be made with certainty. As with other autoimmune rheumatic diseases, the diagnosis depends upon the aggregation of characteristic symptoms, signs, laboratory data, and radiologic findings. The diagnostic value of the following are discussed in more detail below:

• Symmetrical peripheral polyarthritis
• Morning stiffness
• Rheumatoid nodules
• Laboratory features
• Radiographic bone erosions

Symmetric peripheral polyarthritis — Arthritis that affects the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of both hands is the single most characteristic clinical feature of RA (picture 1A-C). However, peripheral polyarthritis is also a common feature of other rheumatic diseases such as systemic lupus erythematosus (SLE), systemic sclerosis (scleroderma), psoriatic arthritis, and rheumatic fever. As a result, this finding alone cannot be used to make a diagnosis of RA. On the other hand, symmetric polyarthritis, particularly of the MCP, metatarsophalangeal (MTP), and/or PIP joints, strongly suggests RA. (See "Evaluation of the adult with polyarticular pain".)

Some patients present with involvement of a single large joint, such as the shoulder or knee. In this setting, the diagnosis depends upon examination of the synovial fluid, additional laboratory tests, and imaging studies. In some cases, further follow-up is required before an accurate diagnosis can be rendered. This is often dependent upon the development of arthritis in the small joints of the hands, the wrist, elbows, or ankle. (See "Evaluation of the adult with monoarticular pain".)