A 32-year-old man is evaluated in the emergency department for a severe occipital headache. He reports flulike symptoms for the past 2 to 3 weeks, with fever, malaise, fatigue, neck stiffness, generalized achiness, sore throat, and mild nausea. He also notes having “swollen glands” in his neck and neck stiffness but no vomiting, abdominal pain, diarrhea, or cough. He indicates that he had a reddish skin rash located across his chest and upper abdomen that first appeared several days after onset of his fevers and other symptoms and began to fade several days ago; the rash was present for approximately 1 week. Medical history is unremarkable, and he takes no medications. The patient thinks he had all standard childhood vaccinations. He is sexually active with both men and women, with intermittent condom use.
On physical examination, the patient appears uncomfortable. Temperature is 38.3 °C (100.9 °F), and other vital signs are normal. No abnormalities are seen on nondilated funduscopic examination. Cervical lymphadenopathy and pharyngeal erythema are noted. A faint maculopapular rash is present on the trunk. The remainder of the examination is unremarkable.
A lumbar puncture is performed.
Leukocyte count | 55/µL (55 × 106/L), with lymphocytic predominance |
Glucose | 70 mg/dL (3.9 mmol/L) |
Pressure (opening) | 80 mm H2O |
Protein | 149 mg/dL (1490 mg/L) |
CSF Gram stain is negative, and culture results are pending.
Which of the following studies is most likely to confirm the diagnosis in this patient?