Psoriatic arthritis Quiz: Ace Your Exams

A 47-year-old woman presents to the primary care office with joint pain and nail changes. She has a four-month history of pain, stiffness, and swelling in her fingers, and left knee. She works as a data entry freelancer, and her worsening symptoms have significantly impaired her ability to work. She has a 10-year history of psoriasis which is well controlled with topical agents. Temperature is 37°C (98.7°F), pulse is 70/min, and blood pressure is 115/73 mmHg. Physical examination shows a few patches of silvery-white scales on the extensor surfaces of the elbows. Examination of the nails shows transverse depressions and subungual hyperkeratosis. Multiple joints of the fingers and toes are tender and swollen, as is the left knee. Laboratory studies show a C-reactive protein (CRP) of 8 mg/L and an erythrocyte sedimentation rate (ESR) of 23 mm/hr. ANA and anti-ccp antibodies are negative. Which of the following will be most helpful for determining the severity of this patient’s arthritis?