A 67-year-old man comes to the emergency department due to 2 days of fever, malaise, headache, and myalgia. He has also noticed a nonpruritic skin rash on his right leg. The patient has had no abdominal pain, vomiting, or diarrhea. Prior medical problems include hypertension, type 2 diabetes mellitus, and chronic obstructive pulmonary disease. He is an ex-smoker and does not use alcohol or illicit drugs. The patient lives in Texas and a week ago returned from visiting family in Connecticut, where he spent most of his time outdoors.
Temperature is 39.4 C (103 F), blood pressure is 124/84 mm Hg, pulse is 102/min, and respirations are 20/min. Examination shows no scleral icterus or lymphadenopathy. Breath sounds are mildly decreased throughout. The abdomen is soft with no hepatosplenomegaly. There is no neck stiffness. A 4-cm, erythematous skin rash with central clearing is present on the right popliteal area.
Laboratory results are as follows:
Chest x-ray reveals no parenchymal opacity or pleural effusion.
Which of the following diagnostic studies is most appropriate for this patient?

Question

A 67-year-old man comes to the emergency department due to 2 days of fever, malaise, headache, and myalgia.  He has also noticed a nonpruritic skin rash on his right leg.  The patient has had no abdominal pain, vomiting, or diarrhea.  Prior medical problems include hypertension, type 2 diabetes mellitus, and chronic obstructive pulmonary disease.  He is an ex-smoker and does not use alcohol or illicit drugs.  The patient lives in Texas and a week ago returned from visiting family in Connecticut, where he spent most of his time outdoors.
Temperature is 39.4 C (103 F), blood pressure is 124/84 mm Hg, pulse is 102/min, and respirations are 20/min.  Examination shows no scleral icterus or lymphadenopathy.  Breath sounds are mildly decreased throughout.  The abdomen is soft with no hepatosplenomegaly.  There is no neck stiffness.  A 4-cm, erythematous skin rash with central clearing is present on the right popliteal area.
Laboratory results are as follows:
 Chest x-ray reveals no parenchymal opacity or pleural effusion.
Which of the following diagnostic studies is most appropriate for this patient?

A 67-Year-Old Man Comes to the Emergency Department Due to 2