A 48-year-old woman comes to the physician because of a 6-month history of swelling and pain of the feet and hands. Physical examination shows swelling of the metatarsals, metacarpals, and proximal phalanges. There is clubbing of the hands. X-rays of the hands and feet show new bone formation. Blood pressure is 140/90. She has a 60-pack-year history of smoking. Which of the following is the next best step in diagnosis?
Anti-cyclic citrullinated peptide antibody assay
Anti-nuclear antibody assay
Bone densitometry
HLA-B27 screening
X-ray screening
