A 55 year old white female presents to you for evaluation of her arthritis. Her symptoms began several years ago with acute pain and swelling in the left ankle. This was followed six months later by pain and swelling in the left wrist and several joints of the fingers. Her review of systems is otherwise completely negative.

Your examination reveals swelling and tenderness in the right 2^nd, left 2^nd and left 3^rd metacarpophalangeal joints (MCPs), and the right 2^nd, left 3^rd and left 4^th proximal interphalangeal (PIP) joints. The right 2^nd DIP joint is also swollen and tender. The left 4^th metatarsal-phalangeal joint (MTP) is subluxed with a plantar callous, but the other MTPs are unremarkable. There is no swelling in the elbows, wrists, knees or ankles. There are no cutaneous findings. Her general physical examination is normal.

1. Choose the test that will be most helpful in confirming your diagnosis:

a. Serum uric acid

b. Rheumatoid factor

c. HLA-B27 antigen

d. Erythocyte sedimentation rate

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