Table 1 List format of the American College of Rheumatology 1987 criteria for the classification of rheumatoid arthritis (RA). At least four criteria must be fulfilled for classification as RA

Criteria	Definition
Morning stiffness	Morning stiffness in and around the joints, lasting at least 1 h

Arthritis of ⩾3 joint areas	Soft-tissue swelling or fluid in at least three of the following areas: the left or right PIP, MCP, wrist, elbow, knee, ankle, or MTP joints

Arthritis of the hand joints	Swelling of the wrist, MCP, or PIP joints

Symmetric arthritis	Simultaneous involvement of the same joint areas (as above) on both sides of the body (at least 50% of affected joint areas affected symmetrically)

Rheumatoid nodules	Subcutaneous nodules present

Rheumatoid factor	Detected by a method that yields positive findings in <5% of normal controls

Radiographic changes	Erosions or unequivocal bony decalcification localised to the joints of the hands and wrists

MCP, metacarpophalangeal; MTP, metatarsophalangeal; PIP, proximal interphalangeal.