A 54-year-old man is admitted to the hospital because of worsening lower extremity swelling and knee and ankle pain and stiffness. These symptoms have made walking very difficult for the past month.
For 18 years, the patient has had hypertension, for which he takes a β-blocker. Otherwise, he has been healthy. He has no known drug allergies. He has smoked 1 pack of cigarettes every 3 days for the past 21 years and drinks alcohol(Drug information on alcohol) in moderation. He denies intravenous drug use. He lives alone and works as a security guard—although for the past month his symptoms have prevented him from performing his job.
Temperature is 38.1oC (100.6oF); heart rate, 104 beats per minute with regular rhythm; respiration rate, 18 breaths per minute; blood pressure, 160/100 mm Hg; and oxygen saturation, 97%. Lungs are clear. There are no oral lesions. Abdomen is normal; results of a digital rectal examination are heme-negative. You note 1+ pitting edema in the lower extremities. Right knee is warm with effusion; left knee is normal. Both ankles are warm and swollen, but the left ankle is more erythematous and edematous and is tender on palpation. Strength is normal throughout, but gait is slow and stiff because of pain in the ankles and knee.
LABORATORY AND IMAGING RESULTS
Blood urea(Drug information on urea) nitrogen level is 11 mg/dL; creatinine level, 1.6 mg/dL; albumin level, 3.5 g/dL; calcium level, 12.1 mg/dL; and phosphorus level, 2.9 mg/dL. White blood cell count is 10,800/μL, and hemoglobin level is 11.1 g/dL. Radiographs of the ankles and right knee show effusion and soft tissue swelling. Aspiration of the knee yields 30 mL of joint fluid, which is sent for analysis.
Which of the following tests is (are) most likely to identify the pathophysiology that underlies the patient’s clinical and laboratory findings?
A. Measurement of rheumatoid factor titer.
B. Serial blood cultures.
C. Measurement of serum parathyroid hormone level (and ionized calcium level).
D. Twenty-four–hour urine collection to assess uric acid excretion.