1 mL serum from a plain red top tube. Allow sample to clot in an upright position for at least 60 minutes, then centrifuge sample and transfer serum to a plastic transport tube within 2 hours of collection. Clearly label tube as serum from a plain red top tube. Refrigerate.
Note: Parallel testing is preferred and convalescent samples must be received within 30 days of receipt of acute samples. Clearly label sample as acute or convalescent.